Transport membrane combustion process with mixer/swirler combustion chamber

ABSTRACT

A combustion system including an ion transport membrane assembly coupled to an internal combustion engine to generate power via oxy-combusting a fuel stream in a combustion chamber of the internal combustion engine, and a method of combusting the fuel stream via the combustion system, wherein a portion of an exhaust stream is recycled to the ion transport membrane assembly. Various embodiments of the combustion system and the method of combusting the fuel stream are disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/295,908 filed Feb. 16, 2016 which is incorporated herein by referencein its entirety.

BACKGROUND OF THE INVENTION Technical Field

The present invention relates to a combustion system including an iontransport membrane assembly coupled to an internal combustion engine togenerate power via oxy-combusting a fuel stream. The present inventionfurther relates to a method of combusting a fuel stream via thecombustion system.

Description of the Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Energy consumptions continue to rise, thus producing more emissions ofCO₂ [Olajire AA, CO₂ capture and separation technologies for end-of-pipeapplications—a review, Energy, 2010, 35, 2610-2628]. Carbon capture frompoint source emissions has been recognized as one of several strategiesnecessary for mitigating the unfettered release of greenhouse gases(GHGs) into the atmosphere. To keep GHGs at manageable levels, a drasticreduction in CO₂ emissions may be needed through capturing andseparation [Perry S, Klemes̆ J. Bulatov I. Integrating waste andrenewable energy to reduce the carbon footprint of locally integratedenergy sectors, Energy, 2008, 33, 1489-1497]. World population growthand the consequent rise in pollution and greenhouse gases emissions areamong the challenging problems that the scientific community must solvein the near future [Amelio M, Morrone P, Gallucci F, Basile A.Integrated gasification gas combined cycle plant with membrane reactors:Technological and economical analysis, Energy Conversion and Management,2007, 48, 2680-2693]. The energy production from fossil fuel sourcesrepresents a large portion (about 65%) of the total greenhouse gasesemissions (carbon dioxide CO₂, methane CH₄ and nitrogen oxide N₂O) [CumoM, Santi F, Simboletti G. Energia, cambiamenti climaticie sequestrodell'anidride carbonica, La Termotecnica, 2003, 33-43]. Besides, mobilesources such as internal combustion engines represent more than 25% ofthe total CO₂ emissions. Most scientists agree that there is a strongconnection between climate change and the anthropogenic emissions ofgreenhouse gases, of which CO₂ is by far the most important gas in termsof the amount emitted. Carbon dioxide is the major atmosphericcontaminant leading to a temperature increase due to the greenhouseeffect. The scientific community considers the anthropogenic CO₂emission needed to maintain the existing world climate condition. As aresult, radical changes in fossil fuel-operated technologies are needed.

Oxy-combustion is among one of the most promising carbon capturetechnologies. Accordingly, a hydrocarbon fuel is burned in a nearly pureoxygen atmosphere, or in a nitrogen-free atmosphere. In view of that,the products of the combustion consist of a mixture of only carbondioxide and water vapor [Nemitallah, M. A., Habib, M. A., Ben-mansour,R., Ghoniem, A. F., Design of an ion transport membrane reactor for gasturbine combustion application, Journal of membrane science, 2014, 450,60-71]. Water vapor can easily be condensed and the resulting carbondioxide can be captured for industrial purposes, or it can be stored.Although this technology is applicable to conventional combustionsystems it needs an oxygen-separating system, wherein oxygen isseparated from air or another oxygen-containing stream. Having anoxygen-separating system as a separate unit for removing undesiredsubstances in oxy-combustion consumes a portion of the output powergenerated by the combustion system [Haslbeck, J., Capicotto, P., Juehn,N., Lewis, E., Rutkowski, M., Woods, M., et al., bituminous coal toelectricity, Washington D.C., DOE/NETL-1291, 2007]. Therefore, utilizingthe oxygen-separating system in a combustion system is not an efficientway to turn a combustion system into an oxy-combustion system.

A new approach for oxy-combusting a fuel has been recently disclosed viathe use of ion transport membrane reactors (OTMR). In these reactors,oxygen is separated from a gaseous mixture (generally air) at atemperature ranging from 650° C. to 950° C., and a fuel is oxy-combustedin the presence of the separated oxygen [Ahmed, P., Habib, M. A.,Ben-Mansour, R., Kirchen, P., Ghoniem, A. F., CFD (computational fluiddynamics) analysis of a novel reactor design using ion transportmembranes for oxy-fuel combustion, Energy, 2014, 77, 932-944].Alternatively, fuel can also be burned in the presence of the separatedoxygen and recycled carbon dioxide, in the permeate side of themembrane. Several membrane materials were shown to effectively separateoxygen from a gaseous mixture. Among those, lanthanum cobaltiteperovskite ceramics, modified proviskite ceramics [Balachandran, U.,Kleefisch, M. S., Kobylinski. T. P., Morissette, S. L., Pei, S., Oxygenion-conducting dense ceramic membranes, US patent, 1997, U.S. Pat. No.5,639,437], brownmillerite structured ceramics [Schwartz, M., White, J.H., Sammels, A. F., Solid state oxygen anion and electron mediatingmembrane and catalytic membrane reactors containing them, US patent,2000, U.S. Pat. No. 6,033,632], ceramic metal dual phase membranes[Chen. C. C., Prasad, R., Gottzmann, C. F., Solid electrolyte membranewith porous catalytically-enhancing constituents (assigned to praxairtechnology), US patent, 1999, U.S. Pat. No. 5,938,822], and thin duelphase membranes, which consists of chemically stable yttria-stabilizedzirconia (YSZ), [Kim, J., Lin, Y. S., Synthesis and oxygen permeationproperties of thin YSZ/Pd composite membranes, AIChE Journal, 2000, 46,1521] have been comprehensively investigated.

In view of the forgoing, one objective of the present invention is toprovide a combustion system including an ion transport membrane assemblycoupled to an internal combustion engine to generate power viaoxy-combusting a fuel stream in a combustion chamber of the internalcombustion engine. The ion transport membrane assembly includes aplurality of ion transport membranes, wherein each separates molecularoxygen from a gaseous mixture exposed thereon. Another objective of thepresent invention is to provide a method of combusting a fuel stream viathe combustion system, wherein a portion of an exhaust stream isrecycled to sweep the molecular oxygen away from a plurality of permeatezones of the ion transport membrane assembly.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect the present disclosure relates to acombustion system, including i) an ion transport membrane assemblyincluding a) a vessel with an internal cavity, b) a plurality of iontransport membranes that separate the internal cavity into a feed zoneand a plurality of permeate zones, wherein the feed zone has a feedinlet and a feed outlet and each permeate zone has a sweep inlet and asweep outlet, ii) a combustion chamber including a) an oxygen inlet, b)a fuel inlet, c) at least one exhaust outlet, wherein the combustionchamber is located downstream of and fluidly connected to the sweepoutlet of the plurality of permeate zones via an oxygen line, iii) arecycle line that fluidly connects the at least one exhaust outlet tothe sweep inlet of the plurality of permeate zones.

In one embodiment, the combustion system further includes a turbochargerincluding a) a compressor fluidly connected to the oxygen line, whereinthe compressor is located downstream of the sweep outlet of theplurality of permeate zones and upstream of the oxygen inlet of thecombustion chamber, b) a turbine fluidly connected to the at least oneexhaust outlet via an exhaust line, wherein the compressor and theturbine are coupled via a shaft.

In one embodiment, the combustion system further includes i) at leastone compartment, ii) at least one piston slidably disposed inside the atleast one compartment, iii) a crack shaft coupled to the at least onepiston, iv) a plurality of apertures disposed on the at least onecompartment to fluidly connect said compartment to the combustionchamber, v) a plurality of valves disposed in the plurality ofapertures.

In one embodiment, the combustion system further includes a heatexchanger located upstream of and fluidly connected to the feed inlet ofthe feed zone via a feed line and downstream of and fluidly connected tothe turbine via the exhaust line, wherein the heat exchanger isconfigured to heat exchange the oxygen-containing stream with theexhaust stream.

In one embodiment, the combustion system further includes i) a condenserlocated downstream of and fluidly connected to the heat exchanger viathe exhaust line configured to separate a liquid phase from the exhauststream, ii) a CO₂ line that fluidly connects the condenser to the sweepinlet of the plurality of permeate zones.

In one embodiment, the vessel is cylindrical with a first and a secondend separated by a side wall along a longitudinal axis of the vessel,and the feed inlet, the feed outlet, the sweep inlet, and the sweepoutlet of the plurality of permeate zones are located on the first endof the vessel.

In one embodiment, the vessel is cylindrical with a first and a secondend separated by a side wall along a longitudinal axis of the vessel,and the feed inlet and the feed outlet are located on the first end ofthe vessel, and the sweep inlet and the sweep outlet of the plurality ofpermeate zones are located on the second end of the vessel.

In one embodiment, the vessel is cylindrical with a first and a secondend separated by a side wall along a longitudinal axis of the vessel,and the feed inlet and the sweep outlet of the plurality of permeatezones are located on the first end, and the feed outlet and the sweepinlet of the plurality of permeate zones are located on the second endof the vessel.

In one embodiment, the vessel is cylindrical with a first and a secondend separated by a side wall along a longitudinal axis of the vessel,and the feed inlet and the sweep inlet of the plurality of permeatezones are located on the first end, and the feed outlet and the sweepoutlet of the plurality of permeate zones are located on the second endof the vessel.

In one embodiment, the vessel is cylindrical with a first and a secondend separated by a side wall along a longitudinal axis of the vessel,and each of the plurality of ion transport membranes has a longitudinalaxis which is substantially parallel to the longitudinal axis of thevessel.

In one embodiment, each of the plurality of ion transport membranes isan elongated tube having a diameter in the range of 5 to 50 mm, a lengthin the range of 0.5 to 5 m, and a wall thickness in the range of 0.5 to3.5 mm.

In one embodiment, at least five ion transport membranes are disposedinside the vessel with an inter-membrane distance of at least 10 mm.

According to a second aspect the present disclosure relates to a methodof combusting a fuel stream, involving i) delivering anoxygen-containing stream to a feed zone of an ion transport membraneassembly, wherein molecular oxygen present in the oxygen-containingstream is transported across a plurality of ion transport membranes to aplurality of permeate zones of the ion transport membrane assembly, ii)delivering the molecular oxygen present in the plurality of permeatezones to a combustion chamber, iii) delivering the fuel stream to thecombustion chamber to combust the fuel stream with the molecular oxygento form an exhaust stream comprising carbon dioxide and water vapor, iv)flowing a portion of the exhaust stream comprising carbon dioxide andwater vapor into the plurality of permeate zones of the ion transportmembrane assembly to form an oxygen-enriched stream comprising themolecular oxygen, carbon dioxide, and optionally water vapor, v)delivering the oxygen-enriched stream to the combustion chamber.

In one embodiment, the method of combusting further involves i) mixingthe oxygen-enriched stream with the fuel stream to form a combustionmixture, ii) delivering the combustion mixture to the combustionchamber.

In one embodiment, carbon dioxide and water vapor are present in theexhaust stream, and the method of combusting further involves i) coolingthe exhaust stream via a condenser to form a liquid phase in the exhauststream, ii) separating the liquid phase from the exhaust stream to forma CO₂ stream and a water stream, iii) flowing a portion of the CO₂stream into the plurality of permeate zones to form the oxygen-enrichedstream comprising the molecular oxygen and carbon dioxide.

In one embodiment, the method of combusting further involves expandingthe exhaust stream in an expander to generate power.

In one embodiment, the method of combusting further involves heatexchanging the oxygen-containing stream with the exhaust stream via aheat exchanger, prior to delivering the oxygen-containing stream to thefeed zone.

In one embodiment, the exhaust stream is flowed into the plurality ofpermeate zones in a direction counter-current to the flow of theoxygen-containing stream in the feed zone.

In one embodiment, the exhaust stream is flowed into the plurality ofpermeate zones in a direction co-current to the flow of theoxygen-containing stream in the feed zone.

In one embodiment, an oxygen-depleted stream having a pressure in therange of 1 to 10 bars egresses the feed zone, and the method ofcombusting further involves expanding the oxygen-depleted stream in anexpander to generate power.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1A is a process flow diagram of a combustion system.

FIG. 1B is a process flow diagram of the combustion system in analternative embodiment.

FIG. 1C illustrates an ion transport membrane assembly of the combustionsystem.

FIG. 1D illustrates a magnified image of an ion transport membrane inthe ion transport membrane assembly.

FIG. 1E illustrates a cross-section of the ion transport membraneassembly.

FIG. 1F illustrates a cross-section of the ion transport membraneassembly in an alternative embodiment.

FIG. 1G illustrates an internal combustion engine of the combustionsystem.

FIG. 1H is a top-view of a cross-section of the internal combustionengine, wherein a combustion chamber and a plurality of compartmentsjoin together.

FIG. 1I is a process flow diagram of the combustion system having theinternal combustion engine.

FIG. 2 represents a P-V diagram of a Carnot cycle.

FIG. 3 represents a P-V diagram of an Otto cycle.

FIG. 4 represents a P-V diagram of a Diesel cycle.

FIG. 5A represents an engine power as function of engine speed at fullload conditions for a pure diesel fuel.

FIG. 5B represents an engine BSCF (Brake Specific Fuel Consumption) asfunction of engine speed at full load conditions for a pure diesel fuel.

FIG. 6 illustrates a square arrangement of the ion transport membranesin the ion transport membrane assembly.

FIG. 7 represents a comparison of an oxygen permeation flux as functionof sweep flux rate, when numerical results [Nemitallah, M. A., A studyof methane oxy-combustion characteristics inside a modified designbutton-cell membrane reactor utilizing a modified oxygen permeationmodel for reacting flows, Journal of Natural Gas Science and Engineering2016, 28, 61-73] are compared to experimental results [Behrouzifar, A.,Atabak, A. A., Mohammadi, T., Pak, A., Experimental investigation andmathematical modeling of oxygen permeation through denseBa_(0.5)Sr_(0.5)Co_(0.5)Fe_(0.2)O_(3-δ) (BSCF) perovskite-type ceramicmembranes, Ceramics international, 2012, 38, 4797-4811].

FIG. 8A represents an axial distribution of the oxygen permeation fluxof the ion transport membrane assembly, when the flow of the feed zoneis co-current and counter-current relative to the flow of the permeatezone.

FIG. 8B represents an axial distribution of the oxygen partial pressurein the feed and the permeate zones of the ion transport membraneassembly, when the flow of the feed zone is co-current andcounter-current relative to the flow of the permeate zone.

FIG. 9A represents an axial distribution of the oxygen permeation fluxof the ion transport membrane assembly, when a fuel stream includes 5%and 10% CH₄.

FIG. 9B represents an axial distribution of the oxygen partial pressurein the feed and the permeate zones of the ion transport membraneassembly, when the fuel stream includes 5% and 10% CH₄.

FIG. 10 represents an axial distribution of the oxygen permeation fluxof the ion transport membrane assembly, at different lengths of the iontransport membranes.

FIG. 11A represents an axial distribution of the oxygen permeation fluxof the ion transport membrane assembly, at different diameters of theion transport membranes.

FIG. 11B represents an axial distribution of the oxygen partial pressurein the feed and the permeate zones of the ion transport membraneassembly, at different diameters of the ion transport membranes.

FIG. 12 represents an axial distribution of the oxygen permeation fluxof the ion transport membrane assembly, at different inter-membrane(pitch) sizes of the ion transport membranes.

FIG. 13A represents a contour plot of an oxygen mass fraction on a planenormal to the flow direction at an axial location of Z=0.4 m.

FIG. 13B represents a contour plot of an oxygen mass fraction on a planenormal to the flow direction at an axial location of Z=0.8 m.

FIG. 13C represents a contour plot of an oxygen mass fraction on a planenormal to the flow direction at an axial location of Z=1.2 m.

FIG. 13D represents a contour plot of an oxygen mass fraction on a planenormal to the flow direction at an axial location of Z=1.6 m.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views.

According to a first aspect the present disclosure relates to acombustion system 100, including an ion transport membrane assembly 102(as shown in FIGS. 1A and 1B).

The term “ion transport membrane assembly” as used herein refers to anassembly having at least a vessel 140 with an internal cavity and aplurality of ion transport membranes 150, configured to separatemolecular oxygen from an oxygen-containing stream 128 s. Accordingly,the plurality of ion transport membranes (ITMs) are disposed inside thevessel 140 such that the internal cavity is separated into a feed zone146 and a plurality of permeate zones 148 (as shown in FIGS. 1A, 1B, and1C).

The vessel 140 refers to a compartment having an internal cavity,configured to hold a gaseous mixture at elevated temperatures andpressures, preferably, at a temperature in the range of 800-1,500° C.,more preferably 800-1,200° C., even more preferably 800-1,000° C. Thevessel 140 may hold the gaseous mixture at elevated pressures in therange of 1-50 bars, preferably 10-30 bars, more preferably 10-20 bars.

In one embodiment, the vessel 140 may be made of quartz, stainlesssteel, nickel steel, chromium steel, aluminum, aluminum alloy, copperand copper alloys, titanium, and the like. In a preferred embodiment,the vessel 140 is made of a high-temperature duty ceramic composite thatcan endure a temperature of up to 1,200° C., preferably up to 1,500° C.,more preferably up to 2,000° C. Exemplary high-temperature duty ceramiccomposite may include, but not limited to, borides, carbides, nitrides,and oxides of transition metals selected from the group consisting ofAl, Si, Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and Th, for example, hafniumdiboride (HfB₂), zirconium diboride (ZrB₂), hafnium nitride (HfN),zirconium nitride (ZrN), titanium carbide (TiC), titanium nitride (TiN),thorium dioxide (ThO₂), tantalum carbide (TaC), and composites thereof.In another preferred embodiment, the vessel is made of a metal or analloy such as stainless steel, nickel steel, chromium steel, aluminum,aluminum alloy, copper and copper alloys, titanium, and the like, and aninterior surface of the vessel may be coated with an oxidation resistantlayer to minimize internal surface oxidation. For example, the interiorsurface of the vessel may be coated with the high-temperature dutyceramic composite, quartz, alumina, Pyrex®, and the like. Although thematerials used to construct the vessel are not meant to be limiting andvarious other materials may also be used.

In one embodiment, the vessel 140 is rectangular having an internalvolume in the range of 0.01-50 m³, or preferably 0.1-20 m³, orpreferably 1-10 m³, or preferably 1-5 m³. Accordingly, the rectangularvessel has a length (L), a width (W), and a height (H), wherein thelength-to-width ratio (i.e. L/W) may be in the range of 1-20, preferably1-10, more preferably 1-5, and wherein the height-to-length ratio (i.e.H/L) may be in the range of 0.05-1, preferably 0.1-0.5, more preferably0.1-0.4, even more preferably 0.1-0.3, and most preferably about 0.2.According to this embodiment, the vessel has a longitudinal axisparallel to a ground surface. In a preferred embodiment, the vessel 140is cylindrical, which is vertically or preferably horizontally oriented.For example, the vessel may be a portion of a pipe. The vessel 140 mayalso have other geometries including, but not limited to, cylindrical,spherical, oblong, conical, and pyramidal.

In some preferred embodiments, the vessel 140 is rectangular orpreferably cylindrical with a first and a second end separated by a sidewall along a longitudinal axis of the vessel, and each of the pluralityof ion transport membranes 150 has a longitudinal axis which issubstantially parallel to the longitudinal axis of the vessel.Preferably, at least five, more preferably at least 10, but no more than50 ITMs are disposed inside the vessel with an inter-membrane distance(i.e. pitch) of at least 10 mm, preferably at least 18 mm, morepreferably 22 mm.

The plurality of ion transport membranes 150 are oriented such that theinternal cavity of the vessel is separated into a feed zone 146 (i.e. aspace inside the vessel and outside of the plurality of ion transportmembranes) and a plurality of permeate zones 148 (i.e. a space insidethe plurality of ion transport membranes) (as shown in FIG. 1E).Alternatively, in another embodiment, the internal cavity of the vesselis separated into a plurality of feed zones 146 (i.e. a space inside theplurality of ion transport membranes) and a permeate zone 148 (i.e. aspace inside the vessel and outside of the plurality of ion transportmembranes) (as shown in FIG. 1F). The ITM assembly may alternatively bereferred to as “a shell and tube assembly”.

The plurality of ion transport membranes 150 may be disposed in variousarrangements relative to each other. For example, in one embodiment, theITMs are disposed such that a cross-section of the ITM assembly has anarrangement as depicted in FIG. 1E, or FIG. 1F. In another embodiment,the ITMs are equally spaced apart from each other having a squarearrangement as depicted in FIG. 6, or a triangular arrangement.Furthermore, the ITMs are equally spaced apart from each other having arandomly arranged configuration.

Preferably, each of the plurality of ion transport membranes 150 is anelongated tube having a diameter in the range of 5 to 50 mm, preferably10 to 30 mm, more preferably 15 to 20 mm. Furthermore, the elongatedtube preferably has a length in the range of 0.5 to 5 m, more preferably1 to 4 m, even more preferably 1.5 to 2 m. A wall thickness of theelongated tube may be in the range of 0.5 to 3.5 mm, preferably 0.5 to 2mm, more preferably 1 to 1.5 mm. Additionally, a surface area of eachITM 150 may be in the range of 0.05 m²-5 m², preferably 0.1-4 m², morepreferably 0.5-3 m², even more preferably 1-3 m². Accordingly, an oxygenflux of each ion transport membrane is within the range of 0.01-0.1mol·m⁻²·s⁻¹, preferably 0.01-0.05 mol·m⁻²·s⁻¹, more preferably about0.03 mol·m⁻²·s⁻¹ at a temperature in the range of 800-1,500° C.,preferably 800-1,200° C., more preferably 800-1,000° C.

In another embodiment, each of the plurality of ion transport membranes150 may be in the form a duct with a rectangular cross-section having across-sectional area in the range of 0.5 to 15 cm², preferably 1 to 8cm², more preferably 1 to 3 cm², wherein the length and the wallthickness of the duct is preferably substantially similar to that of theelongated tube.

In a preferred embodiment, each ITM 150 may have a compressive strengthof at least 50 MPa, preferably at least 100 MPa, more preferably atleast 200 MPa, and may be utilized to prevent a collapse due to anexcessive pressure in the feed zone 146. Each ITM may preferably besecured inside the ITM assembly 102 with bolts and nuts, O-rings (e.g.ceramic or metal rings), and/or gaskets to prevent any leakage from thefeed zone 146 to each of the permeate zones 148 and vice versa.

The ion transport membrane (ITM) 150, used in the ITM assembly,functions to separate oxygen from air or other oxygen-containing gaseousmixtures by transporting oxide ions (i.e. O²⁻) through a membrane thatis capable of conducting oxide ions and electrons at elevatedtemperatures. When an oxygen partial pressure differential is applied onopposite sides of such a membrane, oxygen molecules ionize on onesurface of the membrane and emerge on an opposite side as oxide ions.Then, the oxide ions (i.e. O²⁻) recombine into molecular oxygen (i.e.O₂) on the opposite side, leaving behind free electrons that transportback through the membrane to ionize another oxygen molecule (thisconcept is depicted in FIG. 1D).

Each ITM is a semi-permeable membrane that allows passage of oxide ions(i.e. O²⁻) from the feed zone to the plurality of permeate zones. Theterm “semi-permeable membrane” refers to a membrane that allowsmolecules or ions (in this case oxide ions) with a certain Stokes radiusto pass therethrough by diffusion. Stokes radius of a substance in amembrane refers to the radius of a hard sphere that diffuses at the samerate as that substance through the membrane. Diffusion refers to apassage of the oxide ions through the ITM, and diffusivity is a passagerate of the oxide ions, which is determined by an oxygen partialpressure differential on both sides of the ITM as well as a volumefraction (or a number) of oxide ion vacancies present in the ITM.

Accordingly, the feed zone 146 of the ITM assembly 102 refers to a spaceinside the vessel that is configured to hold an oxygen-containinggaseous mixture. Similarly, the permeate zone refers to a space insidethe vessel wherein molecular oxygen is formed and accumulated. When anoxygen molecule present in the feed zone 146 is contacted with each ITM150, the oxygen molecule may be reduced and an oxide ion (i.e. O²⁻) maybe formed. The oxide ions may transport through each ITM 150 and may becombined with another oxide ion to form molecular oxygen (i.e. O₂) inthe permeate zone.

Each ITM 150 may have a composition with a general formulaA_(x)A′_(x′)B_(y)B′_(y′)O_(3-z), wherein each of A and A′ is selectedfrom the group consisting of Sr, Ba, La, and Ca, and each of B and B′ isselected from the group consisting of Fe, Co, Cr, Ti, Nb, Mn, and Ga.Further, each of x, x′, y, and y′ in the general formula of each ITM hasa value between 0 and 1, such that x+x′=1 and y+y′=1. Also, z is anumber that varies to maintain electro-neutrality of the ITM. Forexample, in some embodiments, each ITM is a perovskite-type ceramichaving a composition of Ba_(u)Bi_(w)Co_(x)Fe_(y)O_(3-δ),Ba_(u)Co_(w)Fe_(x)Nb_(y)O_(3-δ), Ba_(u)Fe_(x)Nb_(y)O_(3-δ),Ba_(w)Ce_(x)Fe_(y)O_(3-δ), Ba_(u)Sr_(w)Co_(x)FeO_(3-δ),Ba_(u)Ti_(w)Co_(x)Fe_(y)O_(3-δ), Ca_(u)La_(w)Fe_(x)Co_(y)O_(3-δ),Sr_(u)Ca_(w)Mn_(x)Fe_(y)O_(3-δ), Sr_(u)Co_(w)Fe_(y)O_(3-δ),La₂NiO_(4+δ), La_(w)Ca_(x)Fe_(y)O_(3-δ), La_(w)Ca_(x)Co_(y)O_(3-δ),La_(u)Ca_(w)Fe_(x)Co_(y)O_(3-δ), La_(w)Sr_(x)Co_(y)O_(3-δ),La_(u)Sr_(w)Ti_(x)Fe_(y)O_(3-δ), La_(u)Sr_(w)Co_(x)Fe_(y)O_(3-δ),La_(u)Sr_(w)Ga_(x)Fe_(y)O_(3-δ), or12.8La_(v)Sr_(w)Ga_(x)Fe_(y)O_(3-δ)—Ba_(u)Sr_(v)Fe_(w)Co_(x)Fe_(y)O_(3-δ),wherein u, v, w, x, and y are each in the range of 0-1, and δ varies tomaintain electro-neutrality. In another embodiment, each ITM is aperovskite-type ceramic having a composition of La_(1-x)Sr_(x)CoO_(3-δ)with x in the range of 0.1-0.7. In some embodiments, each ITM is dopedwith a metallic element selected from the group consisting of Ni, Co,Ti, Zr, and La. Likewise, each ITM may be doped with a metallic elementselected from the lanthanide group of the periodic table (i.e. metallicchemical elements with atomic numbers 57 through 71). Furthermore, eachITM may include a coating layer having a composition of RBaCO₂O_(5+δ),wherein R is a metallic element selected from the lanthanide group (i.e.elements with atomic numbers 57 through 71) of the periodic table.Preferably, R is at least one element selected from the group consistingof Pr, Nd, Sm, and Gd. In a preferred embodiment, each ITM includespores in the size range of 0.1-10 nm, preferably 0.5-5 nm, morepreferably 0.5-3 nm.

In one embodiment, a selectivity of each ITM 150 with respect to oxideions (i.e. O²⁻) is at least 90%, preferably at least 95%, morepreferably at least 98%. Selectivity of an ITM with respect to an ion(e.g. oxide ions) is a measure of the capability of that ITM totransport the ion (e.g. oxide ions) over other substances present in anoxygen-containing gaseous mixture. For example, if selectivity of an ITMwith respect to oxide ions is 99%, then 99 wt % of permeated substancesthrough the membrane are oxide ions. Selectivity of an ITM with respectto oxide ions may be determined by the size of vacancies present in thecrystal structure of each ITM. Oxide ions form in a reduction reactionwhen molecular oxygen is contacted with an ITM in the feed zone 146 andin the presence of free electrons. An ITM having a 100% selectivity withrespect to oxide ions only allows the oxide ions to permeate through themembrane. In one embodiment, a selectivity of each ITM with respect tocarbon dioxide, elemental nitrogen (i.e. N₂), water vapor, carbonmonoxide, argon, and sulfur is less than 5%, preferably less than 2%,more preferably less than 1%, even more preferably less than 0.5%.

The ion transport membrane assembly 102 further includes a feed inlet142 and a feed outlet 144 disposed on the feed zone 146. The feed inlet142 and the feed outlet 144 are utilized as passages for loading andunloading the feed zone 146.

In one embodiment, the feed inlet 142 and the feed outlet 144 aresubstantially similar, wherein each is a cylindrical port having aninternal diameter in the range of 10-80 mm, preferably 10-50 mm, morepreferably 20-50 mm, and is configured to transfer a pressurized streamhaving a pressure in the range of 1-50 bars, preferably 1-30 bars, morepreferably 1-20 bars.

The feed inlet 142 and the feed outlet 144 may be secured perpendicularand/or parallel to the longitudinal axis of the vessel. For example, inone embodiment, the vessel 140 is a horizontally oriented cylindricalvessel, where the longitudinal axis of each of the plurality of ITMs issubstantially parallel to the longitudinal axis of the vessel, and thefeed inlet 142 and the feed outlet 144 are secured parallel to thelongitudinal axis of the vessel (as depicted in FIG. 1C). Alternatively,the feed inlet 142 and the feed outlet 144 may be disposed perpendicularto the longitudinal axis of the vessel (as depicted in FIGS. 1A and 1B).

The ion transport membrane assembly 102 further includes a sweep inlet152 and a sweep outlet 154 disposed on each permeate zone 148. Similarlyto the feed inlet 142 and the feed outlet 144, the sweep inlet andoutlet of each permeate zone are adapted for loading and unloading eachpermeate zone. In one embodiment, each of the sweep inlets 152 and thesweep outlets 154 are substantially similar, wherein each is acylindrical port having an internal diameter in the range of 2-20 mm,preferably 5-10 mm, relative to the diameter of each ITM 150, which isin the range of 5 to 50 mm, preferably 10 to 30 mm, more preferably 15to 20 mm. Preferably, the each of the sweep inlets and the sweep outletsare configured to bear a pressure of up to 50 bars, preferably up to100.

In one embodiment, the vessel 140 is cylindrical with a first and asecond end separated by a side wall along a longitudinal axis of thevessel, and the feed inlet 142, the feed outlet 144, the sweep inlet152, and the sweep outlet 154 of the plurality of permeate zones 148 arelocated on the first end of the vessel. Accordingly, each ITM has aU-shape structure, wherein the inlets and the outlets are located on asame end of the vessel. Having the feed inlet, the feed outlet, and theplurality of sweep inlets and the sweep outlets on one end of the vesselmay provide an extended contact time of each gaseous mixture in the feedand the permeate zones with the ITMs. Furthermore, having all inlets andoutlets on one end may provide a higher contact surface, when comparedto an embodiment where inlets and outlets are located on opposite ends.In another embodiment, the feed inlet and the feed outlet are located onthe first end of the vessel, and the sweep inlet and the sweep outlet ofthe plurality of permeate zones are located on the second end of thevessel. In another embodiment, the feed inlet and the sweep outlet ofthe plurality of permeate zones are located on the first end, and thefeed outlet and the sweep inlet of the plurality of permeate zones arelocated on the second end of the vessel (as depicted in FIGS. 1A and1B). Accordingly, the flow in the feed zone 146 is configured to becounter-current relative to the flow in each of the permeate zones. Inan alternative embodiment, the feed inlet and the sweep inlet of theplurality of permeate zones are located on the first end, and the feedoutlet and the sweep outlet of the plurality of permeate zones arelocated on the second end of the vessel. According to this embodiment,the flow in the feed zone is configured to be co-current relative to theflow in each of the permeate zones. Other than inlets/outlets designedto allow ingress and egress, the vessel may be sealed to prevent anyleakage.

In a preferred embodiment, the combustion system 100 further includes agas mixer 118 located downstream of and fluidly connected to theplurality of the sweep outlets 154 of the ITM assembly 102. The gasmixer 118 may be configured to combine a plurality of streams thategress the plurality of the sweep outlets into a single stream.Furthermore, in another preferred embodiment, the combustion system 100further includes a gas splitter 116 located upstream of and fluidlyconnected to the plurality of the sweep inlets 152 of the ITM assembly102. The gas splitter 116 may be configured to split a single streaminto a plurality of streams and feed the same to the plurality ofpermeate zones 148 via the plurality of the sweep inlets 152.

The ion transport membrane assembly 102 further includes a plurality ofbaffles 156 disposed inside the vessel and secured to the side wall ofthe vessel (as depicted in FIG. 1C). In a preferred embodiment, thebaffles 156 are equally spaced apart in a zigzag arrangement (as shownin FIG. 1C). Having the baffles with a zigzag arrangement may provide alarger residence time of the oxygen-containing stream inside the vessel,when compared to an embodiment where the baffles are not present. Inanother embodiment, the baffles 156 are randomly arranged within thevessel.

In addition, the ion transport membrane assembly may also include someother components such as, a gas feed assembly, one or more flowcontrollers, a manifold, and/or a gas connector.

The combustion system 100 further includes a combustion chamber 108. Thecombustion chamber 108 refers to a sealed vessel, wherein a fuel stream122 s is combusted in the presence of oxygen to form a gaseous mixturehaving an elevated pressure and temperature.

The combustion chamber 108 includes at least one inlet and at least oneoutlet. Preferably, the combustion chamber 108 includes an oxygen inlet162, a fuel inlet 164, and at least one exhaust outlet 166. In apreferred embodiment, the oxygen inlet 162, the fuel inlet 164, and theat least one exhaust outlet 166 are substantially similar to the feedinlet 142 or the feed outlet 144 of the ITM assembly 102.

In one embodiment, the combustion chamber 108 is located downstream ofand fluidly connected to the sweep outlet 154 of the plurality ofpermeate zones 148 via an oxygen line 120. Accordingly, the gas mixer118 is adapted to combine the plurality of streams that egress theplurality of the sweep outlets 154 into a single stream and deliver thesame to the oxygen inlet 162 via the oxygen line 120.

Referring to FIG. 1B. In another embodiment, the combustion chamber 108has an inlet and an outlet, wherein the plurality of streams that egressthe plurality of the sweep outlets are mixed with a fuel stream 122 s ina mixer 107 to form a combustion mixture 123 s, and the combustionmixture is then fed to the combustion chamber 108 via the inlet. Themixer 107 is preferably located upstream of the combustion chamber 108and is fluidly connected to the inlet. The mixer 107 may refer to anoperational unit adapted to mix a plurality of gas streams, preferablyat medium-to-high pressures (i.e. at least 20 bars, preferably at least50 bars), and deliver a mixed stream having a pressure within the rangeof 5-50 bars, preferably 10-30 bars, more preferably 10-20 bars, to theinlet of the combustion chamber 108. According to this embodiment, themixer is configured to mix molecular oxygen or an oxygen-enriched stream120 s with the fuel stream 122 s.

In a preferred embodiment, the combustion chamber 108 further includesone or more swirlers located inside of the combustion chamber andmechanically connected to the inlet or a plurality of inlets (i.e.oxygen inlet 162 and fuel inlet 164). The swirler is configured toexpand and agitate influents of the combustion chamber, and to create avortex of a fluid therein. Having a swirler (or a plurality of swirlers)at the inlet (or a plurality of inlets) of the combustion chamber mayenhance mixing the influents. Further, having the swirler/s may increasea residence time of the influents inside the combustion chamber.

The oxygen line 120 may be a tubular channel that is configured todeliver an oxygen-enriched stream 120 s from the plurality of permeatezones 148 to the inlet (or preferably the oxygen inlet 162) of thecombustion chamber 108. Preferably, the oxygen line 120 may be made of ametal, a metal alloy, or a ceramic composite. Alternatively, the oxygenline may be made of a metal or a metal alloy coated with ahigh-temperature duty ceramic (e.g. alumina), and is configured to beara pressure up to 50 bars, preferably up to 100 bars, even morepreferably up to 150 bars, while also configured to endure a temperatureup to 1,000° C., preferably 1,500° C., more preferably 2,000° C.

The combustion system 100 further includes a recycle line 126 thatfluidly connects said exhaust outlet 166 of the combustion chamber 108to the sweep inlet 152 of the plurality of permeate zones 148. Therecycle line is configured to transport an exhaust stream that egressesthe combustion chamber to the plurality of permeate zones of the ITMassembly. A diameter of the recycle line may vary depending on thevolumetric flow rate of the exhaust stream. Preferably, the recycle linemay have a diameter within the range of 1 to 20 cm, preferably 1 to 10cm. Furthermore, a thickness of the recycle line may vary depending onthe pressure and the temperature of the exhaust stream. For example, inone embodiment, the temperature of the exhaust stream is in the range of600 to 1,000° C., preferably 600 to 1,000° C., wherein the thickness ofthe recycle line is within the range of 2 to 50 mm, preferably 5 to 30mm, more preferably 5 to 20 mm. Additionally, a material type of therecycle line may vary depending on the temperature and the pressure ofthe exhaust stream. For example, in one embodiment, the temperature ofthe exhaust stream is in the range of 600 to 1,000° C., preferably 600to 1,000° C., and the pressure of the exhaust stream is within the rangeof 5-50 bars, preferably 10-40 bars, more preferably 20-40 bars.Accordingly, the recycle line 126 is made of a high-temperature dutymetal or an alloy with an alumina liner that covers an interior of therecycle line. In another embodiment, the recycle line 126 is made of ahigh-temperature duty metal or an alloy, and is configured to bear apressure up to 50 bars, preferably up to 100 bars, even more preferablyup to 150 bars, while also configured to endure a temperature up to1,500° C., preferably 2,000° C., more preferably 2,500° C.

Preferably, the gas splitter 116 is adapted on the recycle line 126 tosplit the exhaust stream 124 s, which egresses the exhaust outlet, intoa plurality of exhaust streams and deliver the same into the pluralityof the sweep inlets.

Referring now to FIGS. 1G and 1H. In a preferred embodiment, thecombustion system 100 further includes a plurality of compartments 170that are fluidly connected to the combustion chamber 108 via a pluralityof apertures 168 and valves (as shown in FIGS. 1G and 1H). Furthermore,the combustion system according to this embodiment includes a pluralityof pistons 172 that are slidably disposed inside the compartments 170.In addition, the combustion system of this embodiment includes a crackshaft 176 coupled to the plurality of pistons 172 via a plurality oflevers 174. An assembly of the combustion chamber 108, and the pluralityof compartments 170, apertures 168, valves, pistons 172, levers 174, andthe crack shaft 176 may be referred to as an “internal combustion engine110”. FIG. 1I depicts a process flow diagram of a combustion system 100,wherein the internal combustion engine 110 is utilized to generatepower. Accordingly, a portion of the exhaust stream 124 s may bedelivered to the compartments 170 via the plurality of apertures in asynchronized manner, which may be adjusted by a control system and thevalves. The exhaust stream, which is in an elevated temperature andpressure, expands in the compartments 170, and pushes the pistons 172,and further drives the crank shaft 176 to produce a shaft work. Theinternal combustion engine 110 may preferably be a two-stroke engine,wherein the shaft work is generated with two strokes (up and downmovements) of a piston during only one crankshaft revolution.

FIGS. 1A and 1B depicts a process flow diagram of a combustion system100, wherein an expander 109 is disposed adjacent to the combustionchamber 108 and is utilized to generate power. In one embodiment, thecombustion chamber 108 together with the expander 109 is also referredto as the internal combustion engine 110. According to this embodiment,the term “expander” may refer to a centrifugal or an axial flow turbine,wherein a pressurized stream (i.e. the exhaust stream) is expanded in anisentropic process (i.e. a constant entropy process) to produce shaftwork when the pressurized stream passes through vanes of said turbine.

The shaft work, which is produced via the internal combustion engine110, may also be utilized to drive a compressor, a generator (forgenerating electricity), a crankshaft of another engine, etc.

In one embodiment, the combustion system 100 further includes aturbocharger 103. The turbocharger 103, which may also referred to as a“turbo”, is a turbine-driven forced induction device that may increasean efficiency of the combustion system by forcing extra oxygen-enrichedstream 120 s (or extra combustion mixture) into the combustion chamber108. Accordingly, the turbocharger 103 includes a compressor 104 fluidlyconnected to the oxygen line 120, and is located downstream of the sweepoutlet 154 of the plurality of permeate zones 148 and upstream of theoxygen inlet 162 of the combustion chamber 108. The compressor 104 maycompress the oxygen-enriched stream 120 s and thus deliver extraoxygen-enriched stream to the combustion chamber 108, leading togenerate more energy by oxy-combusting the oxygen-enriched stream.

The turbocharger further includes a turbine 106 fluidly connected to theat least one exhaust outlet 166 via an exhaust line 124, wherein thecompressor 104 and the turbine 106 are coupled via a shaft 105. As aresult, the exhaust stream 124 s that egresses the combustion chamber108 is utilized to drive the turbine 106 and may further run thecompressor 104 via the shaft 105. Preferably, the exhaust line 124 issubstantially similar to the recycle line 126 (as described previously).

In one embodiment, the combustion system 100 further includes a heatexchanger 112 located upstream of and fluidly connected to the feedinlet 142 of the ITM assembly 102 via a feed line 128 and downstream ofand fluidly connected to the turbine 106 via the exhaust line 124.Accordingly, the heat exchanger 112 is configured to heat exchange anoxygen-containing stream 128 s with the exhaust stream 124 s.

The feed line 128 is a tubular channel that is configured to deliver anoxygen-containing stream 128 s to the feed inlet 142 of the ITM assembly102. Preferably, the feed line 128 may be made of a metal, a metalalloy, or a ceramic composite. Alternatively, the feed line 128 may bemade of a metal or a metal alloy coated with a high-temperature dutyceramic (e.g. alumina), and is configured to bear a pressure up to 50bars, preferably up to 100 bars, even more preferably up to 150 bars,while also configured to endure a temperature up to 500° C., preferably1,000° C., more preferably 1,500° C.

In one embodiment, the combustion system 100 further includes acondenser 114 located downstream of and fluidly connected to the heatexchanger 112 via the exhaust line 124. Accordingly, the condenser 114is configured to separate a liquid phase from the exhaust stream 124 sto form a CO₂ stream 132 s and a water stream 134 s. Furthermore, thecombustion system 100 may include a CO₂ line 132 that fluidly connectsthe condenser 114 to the sweep inlet 152 of the plurality of permeatezones 148. Preferably, the CO₂ line 132 is fluidly connected to the gassplitter 116, wherein the CO₂ stream 132 s is split to a plurality ofCO₂ streams, which is further delivered to the plurality of the sweepinlets.

Preferably, the CO₂ line 132 is substantially similar to the recycleline 126. The condenser may be a heat exchanger, a cooling system, or arefrigeration system, although the condenser type is not meant to belimiting and various other condensers may also be used. Preferably, thecondenser 114 controls whether water vapor is delivered back to the ITMassembly or not. Accordingly, water vapor may be introduced to the ITMassembly when the exhaust stream is delivered to the ITM assemblywithout being condensed in the condenser 114. Therefore, it may bepreferred to condense the exhaust stream to remove water content, anddeliver the CO₂ stream 132 s, which may be free from water vapor,instead of the exhaust stream.

In one embodiment, the combustion system 100 further includes an oxygensupplier located upstream of the ITM assembly 102 and fluidly connectedto the feed inlet 142 via the feed line 128, and is configured to supplyan oxygen-containing stream 128 s to the feed zone 146 of the ITMassembly 102. The oxygen supplier may be an air cylinder or an oxygencylinder. Preferably, it may be a compressor located upstream of andfluidly connected to the feed inlet 142 via the feed line 128, whichdelivers an air stream having a pressure in the range of 1-50 bars,preferably 5-40 bars, more preferably 10-30 bars. In addition, a heatexchanger and/or a heater may be adapted to raise a temperature of theair stream to be within the range of 800-1,200° C., preferably800-1,000° C., before entering the feed zone.

In some alternative embodiments, the oxygen supplier may be a series ofoperational units that turns a gaseous mixture, preferably air, into anoxygen-containing stream 128 s having an oxygen partial pressure of atleast 200 torr, preferably at least 350 torr, more preferably 500 torr,even more preferably at least 600 tort. Furthermore, the oxygen supplierof this embodiment may also adjust the pressure, the temperature, theflow rate, the water content, etc. of the oxygen-containing stream priorto delivering the same to the feed inlet 142 of the ITM assembly 102.For example, in one embodiment, the oxygen supplier includes a strippingunit (or a series of separating units) that separates non-oxygensubstances (e.g. nitrogen, carbon dioxide, and water vapor) present inthe oxygen-containing stream. Or, in another embodiment, the oxygensupplier may further include a dehydrator and/or a dehumidifier, wherebya water content of the oxygen-containing stream is reduced to less than1.0 vol %, preferably less than 0.5 vol %, more preferably less than 0.1vol %, with volume percent being relative to the total volume of theoxygen-containing stream. A pressure of the oxygen-containing stream mayalso be adjusted via an auxiliary compressor in the oxygen supplier tobe in the range of 1-50 bars, preferably 5-40 bars, more preferably10-30 bars, wherein a temperature of the oxygen-containing stream may beadjusted (e.g. by a heater and/or a heat exchanger) to be within therange of 800-1,200° C., preferably 800-1,000° C.

In one embodiment, the combustion system 100 further includes a fuelsupplier located upstream of the combustion chamber 108 and fluidlyconnected to the fuel inlet 164 via a fuel line 122, and is configuredto supply a fuel stream 122 s to the combustion chamber 108.Alternatively, the fuel supplier may supply the fuel stream 122 s to themixer 107, wherein the fuel stream 122 s is mixed with theoxygen-enriched stream 120 s, and the mixed stream is delivered to thecombustion chamber 108. The fuel supplier may be a chemical plant andthe fuel stream 122 s may be a hydrocarbon stream outflowing said plant.For example, the fuel supplier may be a gasification plant that providesa syngas stream as the fuel stream. Alternatively, the fuel supplier maybe a methane reforming plant (e.g. a solar methane reforming plant) thatprovides a syngas stream.

In some alternative embodiments, the fuel supplier may also refer to aseries of operational units that provides a fuel stream 122 s having apredetermined pressure, a predetermined temperature, a predeterminedflow rate, and a predetermined water content. For example, the fuelsupplier may include a dehydrator and/or a dehumidifier, whereby a watercontent of the fuel stream is reduced to less than 1.0 vol %, preferablyless than 0.5 vol %, more preferably less than 0.1 vol %, with volumepercent being relative to the total volume of the fuel stream. Inaddition, the fuel supplier may include a sulfur separator to reduce asulfur content of the fuel stream to less than 500 ppm, preferably lessthan 100 ppm, more preferably less than 50 ppm. Preferably, the fuelsupplier may also include a stripping unit (or a series of separatingunits) that separates non-oxygen substances such as carbon dioxide,water vapor, and preferably nitrogen from the fuel stream. A pressure ofthe fuel stream may be adjusted via an auxiliary compressor in the fuelsupplier to be in the range of 1-50 bars, preferably 5-40 bars, morepreferably 10-30 bars. In addition, a temperature of the fuel stream 104s may be adjusted (e.g. by a heater and/or a heat exchanger) to bewithin the range of 500-1,000° C., preferably 800-1,000° C.

Preferably, the fuel line 122 is substantially similar to the oxygenline 120.

In one embodiment, the combustion system 100 further includes one ormore flow control units to control a volumetric flow rate of anoxygen-enriched stream (that flows inside the oxygen line) based on avolumetric flow rate of a fuel stream (that flows inside the fuel line).In view of that, the flow control unit may include a flowmeter disposedon the oxygen line that is configured to determine the volumetric flowrate of the oxygen-enriched stream to generate a flow rate signal.Additionally, the flow control unit may include a control valve disposedon the fuel line, which is configured to control the volumetric flowrate of the fuel stream. The control valve may be a check valve, a ballvalve, a gate valve, or a diaphragm valves, although the valve type isnot meant to be limiting and various other type of valves may also beused. Furthermore, the flow control unit may include a flow controllerthat is configured to receive the flow rate signal from the flowmeter,and to generate and transmit an output signal to the control valve. Theflow controller may refer to a programmable hardware device that isadapted to adjust the volumetric flow rate of the fuel stream based onthe volumetric flow rate of the oxygen-enriched stream.

In one embodiment, the combustion system 100 further includes anexpander 115 located downstream of and fluidly connected to the feedoutlet 144 of the ITM assembly 102 via an oxygen-depleted line 130, andis configured to expand an oxygen-depleted stream 130 s, which egressesthe feed zone 146, to generate power. In one embodiment, the term“expander” may refer to a centrifugal or an axial flow turbine, whereina pressurized stream (e.g. the oxygen-depleted stream) is expanded in anisentropic process (i.e. a constant entropy process) to produce shaftwork when the pressurized stream passes through vanes of said turbine.The shaft work may further be utilized to drive a compressor, agenerator (for generating electricity), a crankshaft of an engine, etc.

According to a second aspect the present disclosure relates to a methodof combusting a fuel stream 122 s, involving delivering anoxygen-containing stream 128 s to the feed zone 146 of the ITM assembly.

The oxygen-containing stream 128 s refers to a gaseous stream thatincludes oxygen, and may further include nitrogen and less than 1.0 vol%, preferably less than 0.5 vol % of argon, carbon dioxide, neon,helium, hydrogen, and water vapor. Preferably, an oxygen partialpressure of the oxygen-containing stream 128 s may be at least 200 torr,preferably at least 350 torr, more preferably 500 torr, even morepreferably at least 600 torr. Preferably, the method involvescompressing the oxygen-containing stream to have a pressure within therange of 1-50 bars, preferably 5-40 bars, more preferably 10-30 bars. Inaddition, the method may further involve heating the oxygen-containingstream to have a temperature within the range of 800-1,200° C.,preferably 800-1,000° C. A temperature of the oxygen-containing streammay be adjusted via one or more heat exchangers or heaters that arelocated across the feed line (e.g. heat exchangers 112 and 113, as shownin FIG. 1B). Furthermore, a pressure of the oxygen-containing stream maybe adjusted via one or more compressors located across the feed line(e.g. compressor 117, as shown in FIG. 1B). Additionally, the method mayinvolve reducing a water content of the oxygen-containing stream to havea water content of less than 1.0 vol %, preferably less than 0.5 vol %,more preferably less than 0.1 vol % via a condenser located across thefeed line (not shown). The oxygen-containing stream may be delivered tothe feed zone 146 of the ITM assembly via the feed line 128 andpreferably a compressor 117 disposed on the feed line 128 (as depictedin FIG. 1B).

After the oxygen-containing stream 128 s is delivered to the feed zone146, molecular oxygen present in the oxygen-containing stream istransported across the plurality of ion transport membranes 150 to theplurality of permeate zones 148 of the ITM assembly. The molecularoxygen, which is accumulated in the plurality of permeate zones, maycontain less than 1.0 vol %, preferably less than 0.5 vol %, morepreferably less than 0.1 vol %, even more preferably less than 0.01 vol% of nitrogen, argon, carbon dioxide, neon, helium, hydrogen, and watervapor.

The method of combusting further involves delivering the molecularoxygen present in the plurality of permeate zones to a combustionchamber. In view of that, the molecular oxygen is delivered to theoxygen inlet 162 of the combustion chamber via an oxygen line 120, whilepreferably a gas pump, more preferably a compressor 104 is disposed onthe oxygen line to facilitate delivering the molecular oxygen. Themolecular oxygen may preferably be compressed before delivering to thecombustion chamber.

In an alternative embodiment, the method involves delivering themolecular oxygen to the mixer 107 prior, wherein the molecular oxygen ismixed with the fuel stream 122 s to form a combustion mixture 123 s, andfurther delivering the combustion mixture to the inlet (i.e. the fuelinlet 164 or the oxygen inlet 162) of the combustion chamber 108.

The method of combusting further involves delivering the fuel stream 122s to the combustion chamber to combust the fuel stream with themolecular oxygen via an oxy-combustion process to form an exhauststream.

In some embodiments, the fuel stream 122 s refers to ahydrocarbon-containing stream. For example, the fuel stream may be amethane stream, an ethane stream, and/or a syngas stream (i.e. a gaseousstream of hydrogen and carbon monoxide). Besides, the fuel stream mayfurther contain one or more combustible compounds (alkanes, alkenes,alkynes, cycloalkanes, etc.) having a carbon content in the range ofC₁-C₂₀, preferably C₁-C₁₂, more preferably C₁-C₈. Preferably, the fuelstream contains less than 5.0 vol %, preferably less than 2.0 vol % ofnitrogen and water vapor. Furthermore, the fuel stream includes lessthan 500 ppm, preferably less than ppm 100, more preferably less than 50ppm of sulfur. Having a fuel stream with a reduced sulfur content may beadvantageous towards preventing formation of sulfur oxides (SO_(x)) inthe exhaust stream, while a fuel stream with a reduced nitrogen contentmay be advantageous towards preventing formation of nitrogen oxides(NO_(x)) in the exhaust stream. Further to the above, the fuel streammay include traces amount (preferably less than 0.1 vol %) of hydrogensulfide, argon, helium, nitrogen oxides (i.e. nitric oxide, nitrousoxide, nitrogen dioxide), or sulfur dioxide. Preferably, the fuel stream122 s comprises at least 70 vol %, more preferably at least 80 vol %,most preferably at least 90 vol % of the combustible compounds (asdescribed). A pressure of the fuel stream may be adjusted to be in therange of 1-50 bars, preferably 5-40 bars, more preferably 10-30 bars,whereas a temperature of the fuel stream may be adjusted to be withinthe range of 500-1,000° C., preferably 800-1,000° C. The fuel stream 122s may be in a liquid phase and/or in a gaseous phase before entering thecombustion chamber.

In one embodiment, the fuel stream 122 s is expanded and agitated via aswirler located at the fuel inlet 164 of the combustion chamber. Theswirler may create a vortex of the fuel stream inside the combustionchamber.

The exhaust stream 124 s includes carbon dioxide and water vapor, andmay also include less than 1.0 vol %, preferably less than 0.5 vol % ofcarbon monoxide, nitrogen oxides (i.e. nitric oxide, nitrous oxide,nitrogen dioxide), sulfur dioxide, argon, helium, and/or carbonic acid.In one embodiment, the exhaust stream 124 s has a temperature in therange of 500-2,000° C., preferably 1,000-2,000° C., more preferably1,000-1,500° C., and a pressure in the range of 5-50 bars, preferably10-40 bars, more preferably 20-40 bars.

The method of combusting further involves flowing a portion of theexhaust stream 124 s, which may initially be formed by combusting thefuel stream 122 s in the presence of molecular oxygen in the combustionchamber, into the plurality of permeate zones 148 of the ITM assembly toform an oxygen-enriched stream 120 s, which includes the molecularoxygen, carbon dioxide, and water vapor. Flowing the exhaust stream 124s into the plurality of permeate zones 148 of the ITM assembly sweepsaway the molecular oxygen, which has been accumulated in each permeatezone, and thus may effectively increase an oxygen flux of each ITM. Anauxiliary compressor (not shown) located on the exhaust line anddownstream of the turbine 106 may be utilized to flow the exhaust streaminto the plurality of permeate zones of the ITM assembly. Other than themolecular oxygen, carbon dioxide, and water vapor, the oxygen-enrichedstream 120 s may also include less than 1.0 vol %, preferably less than0.5 vol % of carbon monoxide, nitrogen, hydrogen, argon, helium,nitrogen oxides (i.e. nitric oxide, nitrous oxide, nitrogen dioxide),and/or sulfur dioxide. Preferably, an oxygen partial pressure of theoxygen-enriched stream 120 s is at least 600 torr, preferably at least700 torr, more preferably 800 torr, even more preferably at least 1,000torr.

In a preferred embodiment, a gas (or oxygen) analyzer is adapted on theoxygen line 120 to measure an oxygen partial pressure of theoxygen-enriched stream 120 s. Further to the gas analyzer, a bypass line(not shown) is also adapted that fluidly connects the oxygen line 120 tothe recycle line 126. Moreover, a first valve is disposed on the bypassline and a second valve is disposed on the oxygen line. Additionally, acontroller is utilized to receive a signal from the gas analyzer, andgenerate an output signal and transmit the output signal to the valve.Accordingly, in one embodiment, the controller is programmed to closethe first valve (and the bypass line) and to open the second valve (andthe oxygen line), when the oxygen partial pressure of theoxygen-enriched stream 120 s is at least 600 torr, preferably at least700 torr, more preferably 800 torr, even more preferably at least 1,000torr. However, in another embodiment, the controller is also programmedto open the first valve (and the bypass line) and closes the secondvalve (and the oxygen line), when the oxygen partial pressure of theoxygen-enriched stream 120 s is less than 600 torr, preferably less than500 torr. In view of this embodiment, the oxygen-enriched stream 120 sis recycled to the recycle line to via the bypass line and is furtherfed to the plurality of permeate zones of the ITM assembly until theoxygen partial pressure of the oxygen-enriched stream 120 s is at least600 torr, preferably at least 700 torr, more preferably 800 torr, evenmore preferably at least 1,000 torr. At this point, the controllercloses the first valve (and the bypass line) and opens the second valve(and the oxygen line), and the oxygen-enriched stream 120 s is deliveredto the combustion chamber 108.

Having a plurality of ITM tubes in the vessel (i.e. the shell and tubestructure, as described previously) may increase an effective membranesurface area, thus increasing a rate of oxygen permeation via the ITMs.Furthermore, the shell and tube structure of the ITM assembly may easethe process of flowing the exhaust stream to sweep away the molecularoxygen, and to ensure that combustion does not take place inside the ITMassembly.

In one embodiment, the exhaust stream 124 s is flowed into the pluralityof permeate zones 148 in a direction counter-current to the flow of theoxygen-containing stream 128 s in the feed zone 146. In anotherembodiment, the exhaust stream 124 s is flowed into the plurality ofpermeate zones 148 in a direction co-current to the flow of theoxygen-containing stream 128 s in the feed zone 146. In anotherembodiment, the exhaust stream 124 s is flowed into the plurality ofpermeate zones 148 such that the flow of the exhaust stream in theplurality of permeate zones 148 is co-current and counter-current to theflow of the oxygen-containing stream 128 s in the feed zone 146 (i.e.the elongated tubes of the ITM assembly have a U-shape structure).

The exhaust stream 124 s may also be utilized to heat up a processstream in the combustion system 100, or a process stream in a powerplant, a chemical processing plant, or a refining plant. Additionally,the exhaust stream may be utilized to run pneumatic actuators and/orpneumatic systems in a power plant, a chemical processing plant, or arefining plant.

Referring now to FIG. 1B. Preferably, in an alternative embodiment,carbon dioxide and water vapor are present in the exhaust stream 124 s,and the exhaust stream is first cooled via the condenser 114 (asdescribed previously) to form a liquid phase in the exhaust stream. Theexhaust stream 124 s may be cooled to room temperature (i.e. 25° C.),preferably a temperature below room temperature and above water freezingpoint (e.g. 15° C.), at atmospheric pressure to form the liquid phase,which may also contain traces amount of carbonic acid. Subsequently, theliquid phase may be separated from the exhaust stream, for example viathe condenser 114 or a liquid-vapor separator, to form a CO₂ stream 132s and a water stream 134 s. The CO₂ stream 132 s preferably includescarbon dioxide and no more than 0.5 vol %, preferably no more than 0.1vol % of nitrogen, hydrogen, carbon monoxide, argon, helium, methane,ethane, etc. Then, a portion of the CO₂ stream 132 s is flowed into theplurality of permeate zones 148 to form the oxygen-enriched stream 120 sincluding the molecular oxygen and carbon dioxide. Since the CO₂ stream132 s may contain traces amount of substances such as carbon monoxide,nitrogen, hydrogen, argon, helium, nitrogen oxides, sulfur dioxide,etc., the oxygen-enriched stream, which is formed according to thisembodiment, may also include such substances. In one embodiment, theoxygen-enriched stream may also include less than 2.0 vol %, morepreferably less than 1.0 vol % of water vapor.

In a preferred embodiment, the CO₂ stream 132 s is nearly a pure carbondioxide having at least 99 vol %, preferably at least 99.5 vol %, morepreferably at least 99.9 vol % carbon dioxide, and thus the methodfurther involves injecting the CO₂ stream 132 s into a geologicalformation. The CO₂ stream may also be used in supercritical extractionsystems or in processes where a low/medium/high pressure CO₂ stream isneeded.

The method of combusting further involves delivering the oxygen-enrichedstream 120 s to the oxygen inlet 162 of the combustion chamber via theoxygen line 120.

In one embodiment, the method of combusting further involves adjustingthe volumetric flow rate of the fuel stream 122 s based on thevolumetric flow rate of the oxygen-enriched stream via the flow controlunit. In view of that, the volumetric flow rate of the fuel stream isadjusted (preferably via the flow control unit) to be within the rangeof 1-5,000 L/min, preferably 100-3,000 L/min, more preferably 500-2,000L/min. In an alternative embodiment, the volumetric flow rate of thefuel stream is adjusted such that a volumetric flow rate ratio of thefuel stream to the oxygen-enriched stream to be in the range of 0.5-1.5,preferably about 1.

Alternatively, in one embodiment, the method of combusting furtherinvolves mixing the oxygen-enriched stream 120 s with the fuel stream122 s via the mixer 107 to form a combustion mixture 123 s, anddelivering the combustion mixture to the inlet (e.g. the oxygen inlet162 or the fuel inlet 164) of the combustion chamber. The combustionmixture 123 s includes molecular oxygen and at least one hydrocarboncompound selected from the group consisting of alkanes, alkenes,alkynes, cycloalkanes having a carbon content in the range of C₁-C₂₀,preferably C₁-C₁₂, more preferably C₁-C₈. Furthermore, the combustionmixture 123 s may include one or more of hydrogen, carbon monoxide,water vapor, and carbon dioxide, wherein a volume fraction of watervapor in the combustion mixture is less than 0.005, more preferably lessthan 0.001.

The method of combusting further involves expanding the exhaust stream124 s in an expander to generate power. As used herein, the term“expanding” refers to a process whereby a high pressure gaseous streamis delivered to an expander (e.g. an internal combustion engine, aturbine, etc.) to generate power. For example, in one embodiment, theexpander is a turbine and the exhaust stream 124 s is flowed throughvanes of the turbine to drive the turbine and to generate shaft work.

In one embodiment, the exhaust stream 124 s has a temperature in therange of 500-2,000° C., preferably 1,000-2,000° C., more preferably1,000-1,500° C., prior to expanding in the expander, whereas thetemperature drops to a value in the range of 100-1,000° C., preferably500-800° C., after expanding. In addition, the exhaust stream may have apressure in the range of 5-50 bars, preferably 10-40 bars, morepreferably 20-40 bars, whereas the pressure may drop to a pressure ofless than 10 bars, or preferably less than 5 bars, after expanding. As aresult, a liquid phase may form, and the exhaust stream may turn into adouble phase stream (i.e. containing both a gaseous phase and a liquidphase), having less than 1.0 vol %, preferably less than 0.5 vol % ofthe liquid phase.

In a preferred embodiment, the method of combusting further involvesheat exchanging the oxygen-containing stream 128 s with the exhauststream 124 s via the heat exchanger 112, prior to delivering theoxygen-containing stream to the feed zone 146 of the ITM assembly. As aresult of heat exchanging the oxygen-containing stream with the exhauststream, a temperature of the oxygen-containing stream may raise to atemperature in the range of 400-800° C., preferably 600-800° C., whileconcurrently a temperature of the exhaust stream may drop to a value inthe range of 100-500° C., preferably 100-400° C.

In another embodiment, the method of combusting further involves heatexchanging the oxygen-containing stream 128 s with the oxygen-depletedstream 130 s via an auxiliary heat exchanger 113, prior to deliveringthe oxygen-containing stream to the feed inlet 142 of the ITM assembly.As a result of heat exchanging the oxygen-containing stream with theoxygen-depleted stream, a temperature of the oxygen-containing streammay raise to a temperature in the range of 500-1,000° C., preferably800-1,000° C. Heat exchanging the oxygen-containing stream with theoxygen-depleted stream may eliminate the need for an additional processstep to adjust the temperature of the oxygen-containing stream prior todelivering the same to the ITM assembly.

In one embodiment, the oxygen-depleted stream 130 s, which egresses thefeed outlet 144 of the ITM assembly, has a pressure in the range of 1 to10 bars, preferably 5 to 10 bars, and a temperature in the range of600-1,200° C., preferably 800-1,000° C., and the method of combustingfurther involves expanding the oxygen-depleted stream in an expander togenerate power. The oxygen-depleted stream 130 s may include oxygen,nitrogen and less than 1% by volume of argon, carbon dioxide, neon,helium, hydrogen, and water vapor. Alternatively, the oxygen-depletedstream 130 s, which may be rich in nitrogen, may be utilized infertilizer industries. The oxygen-depleted stream 130 s may refer to agaseous stream having an oxygen partial pressure within the range of 10to 400 torr, preferably 50 to 400 torr. In situations where an oxygenpartial pressure of the oxygen-depleted stream is within the range of100 to 400 torr, preferably 200 to 400 torr, then a portion of theoxygen-depleted stream may be recycled to be mixed with theoxygen-containing stream 128 s to be delivered to the feed zone 146 ofthe ITM assembly.

The examples below are intended to further illustrate protocols for thecombustion system and the method of combusting a fuel stream, and arenot intended to limit the scope of the claims.

Example 1

In the following examples, a continuous combustion turbocharged highpressure high power ITM integrated zero emission internal combustionengine, as shown in FIG. 1I, is overviewed. A membrane unit is attachedto the internal combustion engine cycle between the exhaust and theintake manifolds to separate the needed oxygen for combustion utilizingthe heat of the exhaust gases.

The engine exhaust gases at high pressure and high temperature arepassed through a turbine to generate the needed power to drive thecompressor. Then, part of the exhaust gases are passed in the permeateside of the membrane unit to extract oxygen from the air flow in thefeed zone of the membrane and the other part is passed through acondenser to separate CO₂. The oxygen rich gas mixture leaving thepermeate side is compressed to the combustion chamber of the continuouscombustion internal combustion engine. Oxy-combustion process occursinside the ITM assembly and the exhaust gases are only CO₂ and H₂O. H₂Ocan be removed through a simple condensation process and then CO₂ can becaptured and compressed.

To increase the power and efficiency of the internal combustion engine,a continuous combustion ITM assembly is introduced to be integrated withthe piston-cylinder assembly of an ICE. In this case, a common highpressure combustion chamber will be used and a series of inlet valveswill control the timing of the flow to each cylinder. A high pressurecompressor driven through exhaust heat recovery turbine will be used tocompress the oxidizer mixture leaving the ITM unit to the combustionchamber. The cycle of the ICE will be reduced to two strokes, namelypower and exhaust strokes. The high pressure continuous oxy-combustionsystem should result in stable high power high speed high efficiencyICE.

Example 2

This example overviews a method of operating the high pressurecontinuous oxy-combustion system. Accordingly, air enters the upperchannel in the ITM unit (as shown in FIG. 1I) where oxygen is permeatedthrough the membrane from the feed zone to the permeate side. Part ofthe exhaust flue gases leaving the turbine is used to heat up theincoming fresh air in a condenser before introducing it to the ITM unit.The condenser is used to separate H₂O for CO₂ capture. Oxygen depletedair (N₂-enriched air) leaves the channel and can be used for otherpurposes such as fertilizer industry, etc. Oxygen is separated insidethe ITM unit using hot engine exhaust gases as sweep gases and then amixture of CO₂, H₂O and O₂ is introduced to the high pressure continuousITM assembly after compression inside a high pressure compressor. Thepurpose of the sweep gas is to purge the oxygen in order to reduce thepartial pressure of Oz and, thus increase the oxygen flux through themembrane. The necessary heat to activate the membrane for oxygenseparation can be extracted from the exhaust flue gases leaving theturbine as presented in FIG. 1I. The hot gases are then introduced tothe ITM unit in the permeate side. Membrane is heated by the heat fromthe hot exhaust gases and then it is activated for oxygen transport.

Preferably, the temperature of the engine exhaust gases is within theoperating range of the membrane and enough for activating the membranefor oxygen separation. Therefore, failure of the membrane due to excesstemperature is not expected at all because there is no combustionoccurring in the permeate side of the membrane.

The counter-current flow configuration used in the ITM unit has manyinherent advantages over co-current ones. Examination of the partialpressure profile reveals that the partial pressure difference is almostconstant along the reactor length, and the oxygen permeation flux ishigher as compared to the case of co-current flow configuration (higherrecovery ratio). Furthermore, in the counter current flow configuration,the more sensitive region where the permeate partial pressure is lowcoincides with the region where the feed partial pressure is low, whichappears to be a better match-up than the co-current case, where the highfeed matches up with the low permeate.

The presence of a combustion chamber provides a continuous combustion,and therefore the exhaust flow is steady and no need for the use ofaccumulators to make the flow steady and prevent pulsation of the flowin case of conventional ICEs.

Example 3

The continuous combustion feature of the present invention results insteady flow to the turbine and, as a result, stable turbine operation isobtained while generating high output power. The turbine is connectedwith a compressor and the input power to the compressor will beincreased then the turbine output power is increased. A turbinecompressor system is used (turbocharged system), the compressor isdriven using an exhaust gases heat recovery turbine located betweenengine exhaust and the ITM unit. The high pressure exhaust gases leavingthe continuous ITM assembly are passed through a turbine to generate thepower to drive a high pressure compressor. As a result, the exhaustgases leave the turbine at low pressure and moderate temperature thatsuit the operation of the ITM unit. The oxidizer mixture containingleaving the ITM is compressed through the compressor to the highpressure continuous ITM assembly.

Example 4

The oxy-combustion process occurs inside the continuous combustion highpressure ITM assembly of the internal combustion engine. Part of theexhaust gases is recirculated through the ITM unit and the remainingexhaust flow is passed through a condenser to heat up the incoming freshair and separate CO₂ for complete elimination of engine emissions.

This process of combustion results in combustion products consist mainlyof H₂O and CO₂. H₂O is separated inside the condenser and CO₂ iscaptured for sequestration. Based on that, the present invention resultsin a carbon-free ICE. Also, as N₂ is completely excluded from thecombustion process and NO_(x) emissions are inhibited. Based on that,the present invention results in complete elimination of engineemissions.

Example 5

FIG. 2 presents the Carnot heat engine cycle on the P-V diagram. Thecycle assumes no irreversibility within the system and, based on that,Carnot cycle has maximum efficiency when it is compared with a realengine working between the same heat source and heat sink. The cyclecombines four processes including isothermal heat addition, adiabaticexpansion, isothermal heat rejection and adiabatic compression. Thepresent high pressure continuous combustion ITM integrated internalcombustion engine utilizes almost constant pressure power and exhauststrokes in addition to adiabatic expansion and compression processesthrough the turbocharger turbine and compressor, respectively. Based onthat, the performance and output power based on the cycle of the presentinvention will be very similar to those of Carnot cycle. The pressureand temperature inside the ITM assembly remain constant at certain flowrates of fuel and oxidizer. During the power stroke, the intake valve isopened and the power is generated at almost constant pressure throughthe whole power stroke from the top center to the bottom center. Duringthe exhaust stroke, the gases are also removed under almost constantpressure conditions. As a result, more power is generated at high crankshaft revolutions and the system is operated very close to the Carnotcycle and, accordingly, maximum power is generated by the engine. Thisis unlike the case of conventional ICEs where the pressure during thepower stroke is reduced to values close to the atmospheric pressure atthe end of the expansion stroke which results in reduction in the engineoutput power. Based on that, the present high pressure continuouscombustion ITM integrated ICE has high efficiency as compared to theconventional ICEs working on Otto or Diesel cycles which haveefficiencies much less than the Carnot one.

Example 6

In conventional ICEs, Otto (in case of gasoline engine) or diesel (incase of diesel engine) cycles are used. Representations of both cyclesare shown in FIG. 3 and FIG. 4. In an ideal condition, the maximumefficiency of Otto cycle is expressed as follows:

$\eta = {1 - \frac{1}{r^{\gamma - 1}}}$

where r is the compression ratio and x is the specific heat ratio (1.4for air). The range of compression ratio in gasoline engine is from 8 to12. Based on that, the efficiency of a conventional gasoline ICE shouldbe in the range from 56% to 63%.

Also, in an ideal condition, the maximum efficiency of Diesel cycle isexpressed as follows:

$\eta = {1 - {\frac{1}{r^{\gamma - 1}}( \frac{\alpha^{\gamma} - 1}{\gamma ( {\alpha - 1} )} )}}$

where r is the compression ratio, γ is the specific heat ratio (1.4 forair) and α is the cut off ratio (V₃/V₂). The range of compression ratioin diesel engine is from 14 to 22. Based on that, the efficiency of aconventional diesel ICE should be in the range from 59% to 66%. Inaddition, in an ideal condition, the efficiency of Carnot cycle isexpressed as follows:

$\eta = {1 - \frac{T_{L}}{T_{H}}}$

where T_(L) is the low temperature (ambient temperature) and TH is thehigh temperature (combustion temperature). Based on the operatingconditions inside ICEs, the Carnot efficiency can approach higher valuesas compared to conventional gasoline and diesel engines. For example, ifan automobile engine burns gasoline at a temperature of T_(H)=816°C.=1089 K and the ambient temperature is T_(L)=21° C.=294 K, then itsmaximum possible efficiency is about 73%. If we keep in mind that theengine in the present invention is working on a cycle very similar toCarnot cycle, then, the efficiency of the present novel engine will bemuch higher than the efficiency of conventional ICEs. Also, the enginein the present invention is high pressure continuous combustion ICE;then, the combustion (high temperature) is expected to be very high ascompared to conventional ICEs and, as a result, the efficiency of thepresent novel engine is expected to approach 80% when it is compared to63% and 66% for gasoline and diesel engines, respectively.

The above calculations are based on reversible cycles. Consideringirreversibility losses and mechanical and heat transfer losses whichreduce the efficiency in any of the previous cycles to around 55%(relative efficiency) of their values, the comparison of the actualengine efficiency can be presented as shown in Table 1, based on thecompression and cut off ratio given above.

TABLE 1 Comparison of the presently disclosed engine efficiency withconventional Otto and Diesel engines. Otto (spark Diesel ignition(Compression An engine utilizing Parameter engine) ignition engine) thedisclosed cycle Cycle thermal 56-63% 59-66% 73-80% efficiency Actualengine 30-34% 32-36% 40-44% efficiency

Example 7

It is well known that transportation consumes 28% of the total energyconsumption. Thus, utilization of the cycle disclosed herein would save25% of the energy consumption by transportation (7.0% of the total rawenergy). Furthermore, it is well known that more than one-quarter oftotal greenhouse gas emissions comes from the transportation sector.Thus utilization of the currently disclosed cycle would reduce thecarbon dioxide production by 25% of the CO₂ production by transportationsector (6.25% of the total CO₂ production). For example Saudi Arabiaproduces around 500 million ton of CO₂ per year. Utilizing the cycledisclosed herein would reduce this quantity to 400 million ton per year.

Example 8

In the following examples, a continuous combustion turbochargedhigh-pressure high-power ITM-integrated zero-emission internalcombustion engine is designed based on certain structural parameters andoperating conditions. The system utilizes an ion transport membrane(ITM) unit, a high pressure common continuous ITM assembly, an internalcombustion engine (ICE), a compressor-turbine (turbocharger) system anda condenser for CO₂ separation before being captured. The high pressureexhaust gases leaving the continuous ITM assembly are passed through aturbine to generate the power to drive a high pressure compressor.Oxygen is separated from air inside the ITM unit utilizing part of thehot exhaust gases leaving the turbine as sweep gases and, then, amixture of CO₂, H₂O and O₂ are generated at the outlet of the ITM unit.This mixture is introduced to the high pressure continuous ITM assemblyafter compression inside a high pressure compressor. Fuel along with theoxidizer mixture is fed to a common continuous ITM assembly. Theoxy-combustion process occurs inside the continuous ITM assembly in theabsence of N₂. As a result, the combustion products are free of NOxemissions and consist mainly of H₂O and CO₂. The other part of exhaustgases leaving the turbine is passed through a condenser to heat up theincoming fresh air and separate CO₂ for complete elimination of engineemissions. A single continuous combustion high pressure common ITMassembly is used in the present system instead of the conventionalmulti-combustion chambers that are used in conventional ICEs. The numberof strokes of the engine is reduced to two stokes including highconstant pressure power stroke in addition to the exhaust stroke. Thesystem results in high pressure stable oxy-combustion flame in a commoncontinuous fuel flexible ITM assembly.

Example 9

In this section a numerical study is conducted to prove the validity ofintegrating ITM unit with the disclosed high pressure ICE. The measuredexperimental data to characterize engine performance of the singlecylinder variable compression ratio diesel engine used in a previousstudy, El-Kassaby and Nemit-allah [Mohammed EL-Kasab, Medhat A.Nemit-allah, Experimental investigations of ignition delay period andperformance of a diesel engine operated with Jatropha oil biodiesel,Alexandria Engineering Journal 2013, 52, 141-149—incorporated herein byreference], are utilized to explain the present numerical study. In thework by El-Kassaby and Nemitallah, the ignition delay period and engineperformance of a single cylinder diesel engine are investigatedconsidering pure diesel fuel and blends of diesel and Jatropah oilbiodiesel fuels. Only the data of engine performance using pure dieselas a fuel are considered in the present numerical study. The necessaryair flow rate to power the single cylinder diesel engine to produce acertain targeted power was recorded in the experiments. As air containsmainly oxygen plus nitrogen, the oxygen flow rate needed to power theengine is calculated and, instead of nitrogen, a mixture of recirculatedgases is used as sweep gas in the ITM unit to extract ore oxygen throughthe ITM and as energy carrier I the ICE to control the temperature.

FIGS. 5A and 5B shows the distributions of power produced by the singlecylinder diesel engine and brake specific fuel consumption (bsfc) asfunctions of engine speed considering pure diesel fuel [MohammedEL-Kasaby, Medhat A. Nemit-allah, Experimental investigations ofignition delay period and performance of a diesel engine operated withJatropha oil biodiesel. Alexandria Engineering Journal 2013, 52,141-149]. Just one data point is picked up from this figure and based onthe measured data at this point, air flow rate is calculated. Theselected point is at engine speed of 1620 revolution per minute (rpm)which corresponds to output power of 3.255 kW and to bsfc of 0.3767kg/kW/hr. These values of engine performance parameters correspond to ameasured air flow rate of 17.5 kg/hr [Mohammed EL-Kasaby, Medhat A.Nemit-allah, Experimental investigations of ignition delay period andperformance of a diesel engine operated with Jatropha oil biodiesel,Alexandria Engineering Journal 2013, 52, 141-149]. Based on that, 21% byvolume of air is oxygen and 79% by volume is nitrogen, the necessaryoxygen flow rate to drive the single cylinder diesel engine to producepower output of 3.255 kW is 1.1326×10⁻³ kg/s. Based on that, an ITM canbe designed unit to produce this amount of oxygen in order to drive theICE.

Example 10—Structure of the ITM Unit

The aim of the present study is to design an ITM unit for integrationwith an ICE. The idea is to separate oxygen from air using ITM unit and,then, oxygen is introduced to the ICE. In the present disclosure, fuelis burned using the separated oxygen by the membranes in the ICE, andportion of the combustion products, consisting mainly of CO₂ and H₂O, ispassed in the permeate side within the membrane tubes. FIG. 1C shows thedisclosed multi-membrane ITM unit. The ITM unit is of shell and tubedesign. Air is fed to the ITM unit in the shell side and oxygen isseparated from air through the membranes. The recirculated gases (CO₂plus H₂O) act as a diluent inside the ICE to control the flametemperature. The stream of the recirculated gases enters into the ITMunit to be passed within the membranes as presented in FIG. 1C. The airenters to the ITM unit through the shell side and flows in the samedirection as the recirculated gases stream into the volumes surroundingthe ion transport membranes. Air is to fill the volume around themembranes, and the oxygen penetrates from the outside surface to theinside surface of the cylindrical membranes via the mechanism as shownin FIG. 1D. FIG. 6 shows a schematic representation of four adjacentcylindrical membranes in square arrangement. Due to symmetry, quarter ofthe square representation (hatched zone) of the ITM unit is consideredto conduct the numerical simulations in the three-dimensions aspresented in FIG. 6.

Example 11—Oxygen Permeation Model

Based on the oxygen chemical potential differences between the feed andthe permeate sides of the membrane, the surface temperature of themembrane and the membrane ambipolar conductivity, oxygen transfersacross the membrane from the high partial pressure feed zone to the lowpartial pressure permeate side [Hong, J., Kirchen, P., Ghoniem. A. F.,Interactions between oxygen permeation and homogeneous-phase fuelconversion on the sweep side of an ion transport membrane, Journal ofmembrane science 2013, 428, 309-322—incorporated herein by reference].The transport process consists of surface exchange of oxygen atoms onboth sides of the membrane (this process depends on the membranetemperature and the activation energy) and bulk diffusion (this processdepends on the ionic conductivity, chemical potential gradient andmembrane temperature) across the membrane surface. Oxygen permeationthrough a dense mixed ionic-electronic conducting material is limited bysurface exchange resistance, bulk diffusion limitations, or both [Habib,M. A., Nemitallah, M. A., Ben-Mansour, R., Recent development inoxy-combustion technology and its applications to gas turbine ITMassemblys and ITM reactors, Energy and fuels 2013, 27, 2-19—incorporatedherein by reference]. It should be noted that the bulk diffusion will bethe controlling step when the membrane is relatively thick. Theextensively used oxygen permeation equation by Xu and Thomson [Xu. S.J., Thomson, W. J., Oxygen permeation rates through ion-conductingperovskite membranes. Chemical engineering science 1999, 54,3839-3850—incorporated herein by reference] in the literature does notconsider the effects of Reynolds number (flow rates) and sub-stepreaction on membrane both surfaces on oxygen permeation flux. Theequation by Xu and Thomson is derived for mixed ionic electronicconducting ceramics based on the following assumptions: (1) higherelectronic conductivity than the ionic conductivity in perovskites; (2)constant concentrations of electron hole on both surfaces of themembrane; (3) oxygen vacancy diffusion coefficient is only function oftemperature (not function of position); and (4) non sub-step surfacereactions are considered on both sides of the membrane. Based on theseassumptions, the oxygen permeation equation can be expressed as follows:

$\begin{matrix}{J_{O\; 2} = \frac{( {k_{r}/k_{f}} )\lbrack {( {1/{P_{O\; 2}^{''}}^{0.5}} ) - ( {1/{P_{O\; 2}^{\prime}}^{0.5}} )} \rbrack}{\lbrack {1/( {k_{f}{P_{O\; 2}^{\prime}}^{0.5}} )} \rbrack + \lbrack {2{L/D_{v}}} \rbrack + \lbrack {1/( {k_{f}{P_{O\; 2}^{''}}^{0.5}} )} \rbrack}} & (1)\end{matrix}$

where P′_(O) ₂ and P″_(O) ₂ are oxygen partial pressure in feed andpermeate sides, respectively. The coefficients D_(v) and k_(f) and k_(r)represent the diffusion coefficient, forward and reverse reaction rateconstants, respectively. These coefficients can be presented in the formof Arrhenius type equations as follows [Nemitallah, M. A., Habib, M. A.,Ben-Mansour, R., Investigations of oxy-fuel combustion and oxygenpermeation in an ITM reactor using a two-step oxy-combustion reactionkinetics model, Journal of membrane science 2013, 432, 1-12—incorporatedherein by reference]:

$\begin{matrix}{D_{v} = {D_{v}^{0}{\exp ( \frac{- E_{D}}{\overset{\_}{R}\; T} )}}} & (2) \\{k_{f} = {k_{f}^{0}{\exp ( \frac{- E_{f}}{\overset{\_}{R}\; T} )}}} & (3) \\{k_{r} = {k_{r}^{0}{\exp ( \frac{- E_{r}}{\overset{\_}{R}\; T} )}}} & (4)\end{matrix}$

where D⁰ _(v), k⁰ _(f) and k⁰ _(r) are the pre-exponential coefficientsand, E_(D), E_(f) and E_(r) are the activation energies. However, theabove oxygen permeation equation cannot predict accurately the oxygenpermeation flux. The equation should be modified in order to take intoaccount the effects of sub-step surface reactions and feed and sweepflow rates [Behrouzifar, A., Atabak, A. A., Mohammadi, T., Pak, A.,Experimental investigation and mathematical modeling of oxygenpermeation through dense Ba_(0.5)Sr_(0.5)Co_(0.5)Fe_(0.2)O_(3-δ) (BSCF)perovskite-type ceramic membranes, Ceramics international 2012, 38,4797-4811—incorporated herein by reference].

Based on the above oxygen permeation equation, the oxygen vacanciesconcentrations on both membrane surfaces are controlled by the surfaceexchange kinetics of the following elementary surface reactions:

$\begin{matrix}{{{\frac{1}{2}O_{2}} + {V^{\bullet\bullet}o}}\overset{{kf}/{kr}}{rightarrow}{O_{o}^{x} + {2h^{\bullet}}}} & (A) \\{{O_{o}^{x} + {2h^{\bullet}}}\overset{{kr}/{kf}}{rightarrow}{{\frac{1}{2}O_{2}} + {V^{\bullet\bullet}o}}} & (B)\end{matrix}$

The parameter O^(x) _(O) represents the lattice oxygen in the perovskitecrystal structure. However, these two reactions are no longer elementaryas they include many sub-step reactions, like dissociation, oxygenadsorption, charge transfer, recombination and bulk diffusion [Ghadimi,A., Alaee, M. A., Behrouzifar, A., Asadi, A. A., Mohammadi, T., Oxygenpermeation of Ba_(x)Sr_(1-x)Co_(0.8)Fe_(0.2)O_(3-δ) perovskite-typemembrane: experimental and modeling. Desalination 2011, 270,64-75—incorporated herein by reference]. Based on the assumption ofconstant electron hole concentration on both sides of the membrane, thereverse reaction rate of reaction A (forward reaction rate of reactionB) are of zero order. However, the effect of sub-step reactions can beconsidered in terms of oxygen partial pressure and oxygen vacancy. But,the consideration of sub-step reaction order for oxygen vacancy willresult in implicit oxygen permeation equation. Thus, the effect ofsub-step reaction order can be considered in terms of oxygen partialpressure and, accordingly, the oxygen permeation equation can bepresented as follows [Behrouzifar, A., Atabak, A. A., Mohammadi, T.,Pak, A., Experimental investigation and mathematical modeling of oxygenpermeation through dense Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ) (BSCF)perovskite-type ceramic membranes, Ceramics international 2012, 38,4797-4811—incorporated herein by reference]:

$\begin{matrix}{J_{O\; 2} = \frac{( {k_{r}/k_{f}} )\lbrack {( {1/{P_{O\; 2}^{''}}^{n}} ) - ( {1/{P_{O\; 2}^{\prime}}^{n}} )} \rbrack}{\lbrack {1/( {k_{f}{P_{O\; 2}^{\prime}}^{n}} )} \rbrack + \lbrack {{2L} + D_{v}} \rbrack + \lbrack {1/( {k_{f}{P_{O\; 2}^{''}}^{n}} )} \rbrack}} & (5)\end{matrix}$

Equation (5) can be used with reasonable accuracy for oxygen permeation;however, this accuracy can be improved if the effects of feed and sweepflow rates are take into account. Oxygen partial pressure in feed andsweep sides is a direct function of feed and sweep flow rates (Reynoldsnumber in both sides). Thus, the effects of flow rates can be consideredin terms of modified oxygen partial pressure in both sides of themembrane. The modified oxygen partial pressure should be function ofReynolds number [Ghadimi, A., Alaee, M. A., Behrouzifar, A., Asadi, A.A., Mohammadi, T., Oxygen permeation ofBa_(x)Sr_(1-x)Co_(0.8)Fe_(0.2)O_(3-δ) perovskite-type membrane:experimental and modeling, Desalination 2011, 270, 64-75—incorporatedherein by reference]. Based on considering different functions of oxygenpartial pressure and comparisons with their experimental measurements ofa BSCF membrane. Behrouzifar et al. [Behrouzifar, A., Atabak, A. A.,Mohammadi, T., Pak, A., Experimental investigation and mathematicalmodeling of oxygen permeation through denseBa_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ) (BSCF) perovskite-type ceramicmembranes, Ceramics international 2012, 38, 4797-4811—incorporatedherein by reference] introduced the following forms for modified partialpressure of oxygen in membrane feed and sweep sides:

P _(O2)′*=(a′+b′Re′ ^(c′))P _(O2)′  (6)

P _(O2)″*=(a″+b″Re″ ^(c″))P _(O2)″  (7)

Where:

Re′=q′/(πv′λ′)  (8)

Re″=q″/(πv″λ″)  (9)

where a, b, c are constants calculated based on the fittings with theavailable experimental data. Those constants account for the effect offlow rate on oxygen partial pressure on both sides of the membrane tocorrectly predict the oxygen permeation flux. The values of theconstants a, b and c are listed in Table 2. The terms q, v and λ arevolumetric flow rate, kinematic viscosity and distance between airentrance and membrane surface, respectively. Equations 8 and 9 aresubstituted in equations 6 and 7 respectively to calculate the modifiedoxygen partial pressure values. Based on the above expressions, themodified oxygen permeation equation can be expressed as follows[Behrouzifar, A., Atabak, A. A., Mohammadi, T., Pak, A., Experimentalinvestigation and mathematical modeling of oxygen permeation throughdense Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ) (BSCF) perovskite-typeceramic membranes, Ceramics international 2012, 38, 4797-4811]:

$\begin{matrix}{J_{O\; 2} = \frac{( {k_{r}/k_{f}} )\lbrack {( {1/{P_{O\; 2}^{''*}}^{n}} ) - ( {1/{P_{O\; 2}^{\prime*}}^{n}} )} \rbrack}{\lbrack {1/( {k_{f}{P_{O\; 2}^{\prime*}}^{n}} )} \rbrack + \lbrack {2{L/D_{v}}} \rbrack + \lbrack {1/( {k_{f}{P_{O\; 2}^{''*}}^{n}} )} \rbrack}} & (10)\end{matrix}$

TABLE 2 Oxygen permeation model parameters [Behrouzifar, A., Atabak, A.A., Mohammadi, T., Pak, A., Experimental investigation and mathematicalmodeling of oxygen permeation through denseBa_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3−δ) (BSCF) perovskite-type ceramicmembranes, Ceramics international 2012, 38, 4797-4811]. Parameter unitvalue D^(o) _(v) m²/s  5.9807 × 10⁻⁵ k^(o) _(f) m/atm^(n)/s 41.688 k^(o)_(r) mol/m²/s  1.166 × 10⁴ E_(D) J/mol 9.2709 × 10⁴ E_(f) J/mol 1.4668 ×10⁵ E_(r) J/mol 1.0291 × 10⁵ n — 0.25 a′ — 0.1015 b′ — 1.8687 c′ —0.4525 a″ — 0.1891 b″ — 9.3439 c″ — 0.132

Example 12—CFD Modeling

Due to the symmetry of the ITM unit, quarter of the square membrane cellis considered for simulation in the three dimensions. The commercialGambit 2.2 software was used to construct the mesh. Very fine mesh cellswere considered in the vicinity of the membrane in both sides. A meshindependency study was performed. The generated mesh was read by the CFDfluent 12.1 commercial software. Fluent was used to solve the steadyflow mass, momentum, energy and species conservation equations whileconsidering laminar flow regime. The equations can be presented asfollows [Nemitallah, M. A., Habib, M. A., Mezghani, K., Experimental andnumerical study of oxygen separation and oxy-combustion characteristicsinside a button-cell LNO-ITM reactor. Energy 2015, 84,600-611—incorporated herein by reference]:

∇·(ρU)=S _(i)  (11)

∇·(ρUU)=−∇P+μ∇ ² U  (12)

(ρC _(P))U·∇T=∇·(λ∇T)  (13)

∇·(ρUY _(i))—∇·(ρD _(i,m) ∇Y _(i))=S _(i)  (14)

where U represents the flow velocity and S_(i) is a source/sink term toaccount for the transfer of oxygen through the membrane bulk. Theparameters λ, D_(i,m) and Y_(i) represent thermal conductivity,diffusion coefficient and species mass fraction, respectively. Thesource/sink term can be presented as function of the calculated oxygenpermeation flux based on equation (10) as follows:

$\begin{matrix}{{{S_{i} = {\frac{{J_{O\; 2} \cdot A_{{cell}.}}{MW}_{O\; 2}}{V_{cell}}\mspace{14mu} {at}\mspace{14mu} {membrane}\mspace{14mu} {permeate}\mspace{14mu} {side}}},{and}}{S_{i} = {{- \frac{{J_{O\; 2} \cdot A_{{cell}.}}{MW}_{O\; 2}}{V_{cell}}}\mspace{14mu} {at}\mspace{14mu} {membrane}\mspace{14mu} {feed}\mspace{14mu} {side}}}} & (15)\end{matrix}$

where, J_(O2) is defined as the oxygen flux through the membrane inmol/m²/s, MW_(O2) is the oxygen molecular weight and A_(cell) andV_(cell) are the area and volume of the cell, respectively. This term isa sink term is feed zone (disappears) of the membrane and a sink term inthe permeate side (appears). This term is applied only to the membraneboundary cells and it is zero elsewhere in the computational domain.Also, the term is applied only to oxygen and it is zero for otherspecies. However, fluent software alone cannot account for oxygenpermeation across the membrane. Instead, a series of user definedfunctions (UDFs) were written in visual C++ and compiled and hooked tothe fluent software. The UDFs modify only in the source term in theconservation equation for only oxygen molecules and only to the cells incontact with the membrane surface in both sides. The membrane surfacewas considered as a grey body with an emissivity of 0.8 and a thermalconductivity of 4 W/m/K [Nemitallah, M. A., Habib, M. A., Mezghani, K.,Experimental and numerical study of oxygen separation and oxy-combustioncharacteristics inside a button-cell LNO-ITM reactor. Energy 2015, 84,600-611]. Due to its stability while performing the calculations thesemi-implicit method for pressure-linked equations (SIMPLE) algorithmwas applied to account for coupling between pressure and velocity fields[Patankar. S. V., Numerical heat transfer and fluid flow. Hemispherepublishing corporation 1980, Washington D.C.]. The second order upwindscheme was used to discretize the convective terms in the conservationequations. The solution was carefully monitored and the solution wasconsidered converged when the residuals of all variables were droppedbelow 10⁻⁶.

Radiation heat transfer modeling should be modeled in ITM simulations inorder to control temperature. The discrete ordinate (DO) radiation modelwas applied in order to solve for the radiative transfer equation (RTE).In order to correctly predict the temperature, the radiation heattransfer vector gradient is calculated and substituted in theconservation equation of energy once the radiation intensity iscalculated. Species transport model was applied to account for massfractions distributions within the computational domain.

The model is validated based on the experimental measurements byBehrouzifar et al. [Behrounfar, A., Atabak, A. A., Mohammadi, T., Pak,A., Experimental investigation and mathematical modeling of oxygenpermeation through dense Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ) (BSCF)perovskite-type ceramic membranes, Ceramics international 2012, 38,4797-4811] and very good agreement with the experimental data wasobtained as shown in FIG. 7. The details of the validation study can befound in our previous work, Nemitallah [Nemitallah, M. A., A study ofmethane oxy-combustion characteristics inside a modified designbutton-cell membrane reactor utilizing a modified oxygen permeationmodel for reacting flows, Journal of Natural Gas Science and Engineering2016, 28, 61-73].

Example 13—Operating Conditions of the ITM Unit

As mentioned above, one data point is selected from the measured data ofengine performance. The selected point is at engine speed of 1620revolution per minute (rpm) which corresponds to output power of 3.255kW and to bsfc of 0.3767 kg/kW/hr. These values of engine performanceparameters correspond to a measured air flow rate of 17.5 kg/hr[Mohammed EL-Kasaby. Medhat A. Nemit-allah, Experimental investigationsof ignition delay period and performance of a diesel engine operatedwith Jatropha oil biodiesel, Alexandria Engineering Journal 2013, 52,141-149]. Based on that 21% by volume of air is oxygen and 79% by volumeis nitrogen, the amount of oxygen flow rate to drive the single cylinderdiesel engine to produce power output of 3.255 kW is 1.1326×10⁻³ kg/s.Based on that, an ITM unit can be designed to produce this amount ofoxygen in order to drive the ICE. In all considered cases for numericalsimulations, the exhaust gases out of the ICE are recirculated to thepermeate side inlet of the ITM unit at temperature of 900° C. Theexhaust gases introduced to the permeate side of each membrane unitconsist of CO₂ and H₂O plus small fraction of methane. Based on previousnumerical results [Nemitallah, M. A., Habib, M. A., Ben-Mansour, R.,Ghoniem, A. F., Design of an ion transport membrane reactor for gasturbine combustion application, Journal of membrane science 2014, 450,60-71; Habib, M. A., Nemitallah, M. A., Design of an ion transportmembrane reactor for application in fire tube boilers, Energy 2015, 81,787-801] and in the works done by Mancini ad Mitsos [Mancini N., Mitsos,A., Ion transport membrane reactors for oxy-combustion Part II: Analysisand comparison of alternatives, Energy 2011, 36, 4721-4739; Mancini N.,Mitsos, A., Ion transport membrane reactors for oxy-combustion e Part I:intermediate fidelity Modeling, Energy 2011, 36, 4701-4720], thedimensions and the flow rates in feed and permeate sides of eachcylindrical membrane are specified. In addition, detailed numericalstudy is performed considering nine simulation cases to determine thedesign and flow conditions as presented in Table 3.

TABLE 3 Representation of flow and design conditions for all simulationcases. Case 1 2 3 (base) 4 5 6 7 8 9 Flow con- Counter currentCo-current figuration Inlet tem- 1173 perature [K] Feed air 2.961 × 10⁻³flow rate [kg/s/cell] Pitch 22 18 22 [mm] Membrane 17 10 24 tubediameter [mm] Membrane 1.8 0.9 3.6 1.8 length [m] Total 2.576 × 10⁻⁴5.152 × 10⁻⁴ 2.576 × 10⁻⁴ 5.152 × 10⁻⁴ 2.576 × 10⁻⁴ permeate flow rate[kg/s/cell] Volume 10% CH₄   5% CH₄ 10% CH₄   5% CH₄ 10% CH₄ fractions45% CO₂ 47.5% CO₂ 45% CO₂ 47.5% CO₂ 45% CO₂ of 45% H₂O 47.5% H₂O 45% H₂O47.5% H₂O 45% H₂O permeate flow

Example 14—Co-Current Vs. Counter-Current Flow Configurations

FIGS. 8A and 8B shows the effect of flow configuration, co-current (case3) and counter-current (case 1), on the axial distributions of: (a)oxygen permeation flux and (b) oxygen partial pressure in feed andpermeate sides of the membrane. More uniform oxygen permeation flux isencountered in case of co-current flow configuration. Also, the partialpressure differences are higher in case of co-current as compared tocounter-current flow configuration as shown in FIGS. 8A and 8B. So, theco-current flow configuration has better characteristics thancounter-current flow configuration. Based on that, the numericalcalculations of the operating and design conditions of the ITM unit areperformed considering co-current flow configuration.

Example 15—Effect of Inlet Fuel Concentration

Effects of inlet fuel concentration, 5% CH₄ (case 4) and 10% CH₄ (case3), on the axial distributions of: (a) oxygen permeation flux and (b)oxygen partial pressure in feed and permeate sides of the membrane arepresented in FIGS. 9A and 9B. Accordingly, the uniformity of oxygenpermeation flux is better at lower fuel concentrations. It's alsopreferred to lower the amount of fuel at membrane unit inlet as the mainfuel is injected in the ICE.

Example 16—Effect of Membrane Tube Length

Oxygen permeation flux was calculated considering three different valuesof membrane length including 0.9 m, 1.8 m and 3.6 m as presented in FIG.10. The membrane unit with a length of 0.9 m resulted in the highestaverage oxygen permeation flux. On average, 0.03 mol/m²/s of oxygen fluxis permeated across the membrane for the case of 1.8 m of membranelength.

Example 17—Effect of Membrane Tube Diameter

Effects of membrane diameter on distributions of oxygen permeation fluxand oxygen partial pressure are also examined considering differentvalues of membrane diameter including 10 mm, 17 mm and 24 mm, and theresults are presented in FIGS. 11A and 11B. For membrane diameter of 17mm, the oxygen permeation flux was the highest among all tested membranediameters as shown in the figure.

Example 18—Effect of Membrane Tube Pitch

Influence of pitch distance between membrane tubes including P=18 mm(case 7) and P=22 mm (case 3) on the axial distributions of oxygenpermeation flux is presented in FIG. 12. Better permeation flux isobtained for the case of 22 mm membrane pitch.

Example 19

Based on the above numerical results, case (4) revealed a desired massflux of oxygen. A flow rate of 5.15212×10⁴ kg/s is introduced to eachmembrane cell at the permeate side with volumetric concentrations of 5%,47.5% and 47.5% for methane. CO₂ and H₂O, respectively. Air (21% oxygenand 79% nitrogen) is fed to the shell side of the membrane unit at flowrate of 2.960619×10⁻³ kg/s for each membrane cell. Each cylindricalmembrane has a diameter of 17 mm and a length of 1.8 m with membranepitch of 22 mm. The contour plots of oxygen mass fractions on planesnormal to flow direction at different axial locations, (a) Z=0.4 m, (b)Z=0.8 m, (c) Z=1.2 m and (d) Z=1.6 m, for the preferred design case(case 4) are presented in FIGS. 13A, 13B, 13C, and 13D. On average, thepermeated oxygen flux in this case is 0.03 mol/m²/s. So, for eachmembrane cell, a total permeation flow rate of oxygen of 2.88252×10⁻³molls is obtained corresponding to 9.22404×10⁻⁵ kg/s. However, theamount of oxygen to operate a single cylinder diesel engine at speed of1620 rpm to produce output power of 3.255 kW is 1.1326×10⁻³ kg/s. Basedon that, a total number of 12.3 membrane cells (13 membrane tubes) withlength of 1.8 m are needed to produce the specified amount of oxygen tofully burn diesel fuel in the single cylinder diesel engine.

1: A method of combusting a fuel stream comprising: delivering anoxygen-containing stream to a feed zone of an ion transport membraneassembly, wherein molecular oxygen present in the oxygen-containingstream is transported across a plurality of ion transport membranes to aplurality of permeate zones of the ion transport membrane assembly;delivering the molecular oxygen present in the plurality of permeatezones to a combustion chamber; delivering the fuel stream to thecombustion chamber to combust the fuel stream with the molecular oxygento form an exhaust stream comprising carbon dioxide and water vapor;mixing the molecular oxygen and the fuel stream with one or more of (i)a mixer disposed upstream of the combustion chamber and (ii) a swirlerdisposed inside the combustion chamber; heat exchanging theoxygen-containing stream with the exhaust stream via a heat exchanger,prior to delivering the oxygen-containing stream to the feed zone;flowing a portion of the exhaust stream comprising carbon dioxide andoptionally water vapor into the plurality of permeate zones of the iontransport membrane assembly to form an oxygen-enriched stream comprisingthe molecular oxygen, carbon dioxide, and optionally water vapor; anddelivering the oxygen-enriched stream to the combustion chamber. 2: Themethod of claim 1, further comprising: mixing the oxygen-enriched streamwith the fuel stream to form a combustion mixture, and delivering thecombustion mixture to the combustion chamber. 3: The method of claim 1,wherein carbon dioxide and water vapor are present in the exhauststream, and the method further comprises: cooling the exhaust stream viaa condenser to form a liquid phase in the exhaust stream; separating theliquid phase from the exhaust stream to form a CO₂ stream and a waterstream; and flowing a portion of the CO₂ stream into the plurality ofpermeate zones to form the oxygen-enriched stream comprising themolecular oxygen and carbon dioxide. 4: The method of claim 1, furthercomprising: expanding the exhaust stream in an expander to generatepower.
 5. (canceled) 6: The method of claim 1, wherein the exhauststream is flowed into the plurality of permeate zones in a directioncounter-current to the flow of the oxygen-containing stream in the feedzone. 7: The method of claim 1, wherein the exhaust stream is flowedinto the plurality of permeate zones in a direction co-current to theflow of the oxygen-containing stream in the feed zone. 8: The method ofclaim 1, wherein an oxygen-depleted stream having a pressure in therange of 1 to 10 bars egresses the feed zone, and the method furthercomprises expanding the oxygen-depleted stream in an expander togenerate power. 9-20. (canceled)